Can you try bandaging the wound? Vet wrap works well on birds. You can put something else over the wound and then wrap with the vet wrap. It sticks to itself, but not to the feathers and has some give to it. It looks kind of like a colored ace bandage rolled up and is sold in a lot of places that sell livestock supplies. Plus vets have it.
I think I just skimmed through a thread about a person that used a woman's mini-pad underneath vet wrap. With the sticky side up against the vet wrap, it kept the pad from shifting. I've never tried that. I've just used plain cotton wound pads under the vet wrap on my dogs.
I don't know what else to suggest. Avian vets do have bird sized anti-pick cones, if you really want to try one. I wonder how he'd like to be fitted with a shirt??? Or would that be a vest? I'm guessing he won't like ANY of these ideas. Good luck on whatever you try.
