Here is the website of an eclectus breeder in the UK -
http://eclectusparrot.co.uk/page-e.htm. Some diet tips are on there.
I am still learning what, and what not, to feed our eccie, Frankie. As far as supply is concerned, it isn't too difficult as we already feed a varied diet to all of our birds - shopping is fairly straightforward as it is basically what we buy for ourselves. We just feed different amounts of the food groups to our different birds and mix it up to provide variety.
Frankie's previous carers didn't actually do much caring as far as we can tell. That is particularly true of his diet and it is one of the main things that we are addressing. His toe nails were very overgrown, and whilst they have been sorted out by his avian vet, allowing him to perch and climb around confidently, he doesn't hold food in his foot like most larger birds do. I don't know if that is just him, or if it is normal eccie behaviour. Our Jardine Jessie, who is about half of Frankie's weight will happily grab a big chunk of food in her foot and chew away. We cut Frankie's food a little smaller, so that he can easily eat straight from bowl to beak (and more recently from fingers to beak). Perhaps foot to beak will come again later, once he gets used to his better foot freedom
All of our birds love big chunks of food on a metal kebab skewer. I have seen them sold in pet shops (particularly ones with good bird accessory stock) as "Kebobs" too. They are great fun for them. We're told not to play with our food, but we positively encourage it with our birds. Foraging for food is stimulating and it can be as simple as wrapping a piece of food in a small piece of paper or a dark green leaf. Many bird toys have nooks and crannies that will take pieces of food and some are designed specifically for that purpose.
At the beginning of the day when breakfast is served, we don't just put the bowls in Frankie's cage. We hold it at the end of a perch and encourage him to take it from there. It took us a few days to get to this stage and Ollie probably isn't ready yet, but it will come. Frankie would look under the bowl, see our fingers, say "Yeah, I'm not stupid!" and back away, but that soon stopped, especially for his first feed of the day. When Frankie knows the food is coming, he is bobbing with excitement waiting for it. He is getting over his "finger fear" very quickly and has now progressed to the stage when he will gently take some foods from our fingers, in or out of his cage. We're very proud of his progress!
I think the basic rule with a lot of birds, not just eccies, is that if it good for you, it is good for your birds, certainly as far as fruit and veg goes.
There are a few exceptions, like onions (incl garlic), avocado and tomato which should not be provided. I've heard a few people feed tomato - we avoid. Clearly, the snacks and treats we eat ourselves (if we are honest!) are generally bad for birds, if not highly dangerous. Fried chips/crisps, crackers that are loaded with salt, chocolate and sugar-high sweets/candy - all very very bad. Most drinks are off the menu too, like coffee & regular tea. We do give our birds camomile tea occasionally - organic and a very weak dilution, cooled to room temperature. A lot of wild birds eat flowers. I've seen plenty of "flower teas" in our asian supermarket, but I believe that most of them contain preservatives or - what's the word? - non-clotting or drying agents? Something like that. We avoid.
High on veg (80%+), low on fruit and even lower on seed and nuts. Eccies need more fibre than most birds. Beans and pulses are good and it looks like you are already feeding those. All of our birds love it.
Green veg and dark green salad leaves (e.g. rocket) are very good. Celery doesn't have much nutritional value but it is crunchy and cool. Give your lad peas in the pod and watch them get destroyed once he's got the hang of them. Mange tout and sugarsnaps should be popular too. Our birds don't care much for broccoli, but if we finely chop it and add it to the bean/pulses mix, it all disappears. A slice of corn on the cob will get shredded too. Baby sweetcorn goes down well. Kale, spinach and the big leaf watercress - dark green again. We buy carrots with the leaves on top - another favourite. Frankie shreds the leaves in seconds and our budgies love hanging from them as they eat them. Most birds, including eccies, like peppers too, from the big bell type down to the small fiery chillis. Cucumber is good too.
A small amount of parboiled butternut squash and/or sweet potato (not white potato) can be served separately or mashed and added to your bean/pulse mix as well.
Fruit - the more exotic the better. All of our birds get apple and pear, which they love, oranges (clementines, satsumas, etc), melon, kiwi, papaya, mango, pomegranate, banana, grapes (seedless preferred), peaches, apricots and berries like strawberry, blueberry, blackberry. Try figs if you can them as wild eccies eat those too. Large fruit stones (peach, apricot, etc) and fruit seeds (apple, pears, oranges, etc) should not be served and discard the leaves as some of them are poisonous.
Sprouts from beans/pulses is another popular food that can be prepared at home. We don't do this yet, but it is very nutritious so we should get organised and do that as well.
Rice (I'd go for brown rather than white) is a good one. We avoid wholewheat pasta for now, but it is fine for some birds - not sure about eccies yet.
Some people provide scrambled egg although we normally only give the hard boiled egg white as the yoke is high in fat. Some people says it's fine occasionally though. Steamed white fish or chicken is good for protein - recommended by an eccie breeder - a small amount every week or so. A small piece of lightly toasted multi-grain bread crust goes down well. Again, this would be an occasional treat.
I've barely scratched the surface. There are plenty more foods that can be served. I dare say it all looks a bit daunting, but you soon get used to it. Provide some variation each day and your Ollie will appreciate that. Demonstrate to him that you are the provider of all of this wonderful food and he will gradually love you more and more.