what about wingless fruit flies?
Get a culture from a university or online and put them in a bowl in the aviary. They are good for quails too
Flour weevil larvae can be cultivated easily. Get a new 40 litre plastic rubbish bin and add 5-10kg of any sort of wheat flour. Put the lid on and leave it for 6 months. Then scoop some flour out and sieve it back into the bin. Put weevil larvae from the sieve into a bowl and feed to birds. If you have several bins of flour, you can harvest from one for a bit while the other repopulates.
You can do the same with rice or any old seed. Find a bag of rice or seed at a supermarket that has stringy web like filaments in it and that is your starter culture. Put that and more rice in a bucket with a lid and it will quickly become infested with weevils. Just don't feed any old seed or grain to the birds.
*NB* keep this culture away from your normal bird seed or it will become infected too.
If you have any old clothes, you can put them into a plastic bin and leave for months. Clothes moths will infest the clothing and in warmer weather the adult moths will come out and fly around and land everywhere. The moths are pretty slow and like dark spots so tend to fly into corners where birds can get them.
*NB* don't keep them in the house or they get into everything and all your clothes become infested.
Having plants in the aviary will attract insects and having a low wattage night light will attract moths and provide some light for the birds to see where they are going if they are startled during the night. Some birds even wake up late at night and have a moth nightcap before going back to bed.