For now if you must hand feed him, get goats milk (I got some powdered at the petstore) and some infant rice cereal. Maybe some apple juice to mix in the water too if he's not drinking. (You may have to force feed him water too at first). This will help him get nutrients hes not getting since he's not eating. You can also try regular yogurt to help his digestive system. (I would go with the goats milk/infant rice cereal first, then when he eats on his own do yogurt every other day until he's much better).
Like GrayRodent said Mazuri is awesome; its what I use. Another good brand is Oxbow, and they also carry a Critical Care diet food too (although its not in my local pet stores), which is why I came up with the above. Just feed him in increments and aim for the side of his mouth (so you don't choke him or anything). I hope he feels better!