I do not think we have qualified vets for birds in where I reside (country = UAE), they are usually qualified for dogs and cats. I will try this weekend though. Until then, is there anything else I can do? I have only started placing him beside the window recently, is that enough or I still need those UVA/UVB bulbs?
Falconry I believe is a major sport in your country. I bet one of the bird of prey vets would be competent to see an amazon or they can recommend someone who is.
Amazons usually wean themselves fairly easily, which to me means he may very well be sick. Otherwise, if he's weak or crying like a baby, feed him. Get a gram scale and weigh him daily so you know if he's gaining or loosing and exactly how much he's gaining or losing. If he was looking good on 2 syringe feedings a day, continue with that while you wait on an appointment with the vet. You can try cooked and soft veggies. Toward the end of weaning when I'm trying to get my babies to give up the syringe for good, I do a lot of cooked until soft sweet potato mixed with a little bit of cooked soft rice, oatmeal and banana. Served warm at a safe hand-feeding temperature. You might have to get him started by offering a clump from your hands, but most birds will take it.
The eyes fading to orange is normal. Most amazons with a lot of yellow on their head have orange eyes. I have to kind of wonder if he was younger than 4 months when you got him because I breed a very similar species to yours and most of mine are clearly starting to get orange eyes by the time they are 4 months old. If yours had solid black eyes when you got him, I bet he was under 4 months. In which case 2 hand-feedings a day might not have been enough to support growth and a feeling of security and it has delayed his whole weaning process. That said, often times a bird that just will not wean on its own has a bacterial infection that needs to be treated. Almost any vet should be able to do a grams stain of his mouth and feces. Better yet would be a culture and sensitivity to diagnose what bacteria are growing in there. Definitely check into the falconry vets. If you can't find one, talk to a dog or cat vet or look up falconry in your country and see if there are any clubs close to you. A lot of arab countries take their falconry birds VERY seriously.