First of all taking it to a vet IS practical advice. You can't expect to keep posting this problem until you get an the answer you WANT to hear.
There is really not much else that anyone can offer you in the way of advice and I am sure that one of the vets that "does not cater to turtles" could at the very least get you the antibiotics that you obviously need for this animal that would appear to be suffering from some sort of bacterial infection.
But we can't diagnose a situation over the internet. Only a vet will be able to help you and since that is not an option -- what more can we tell you?
There are no over counter drugs that you can get that will do more than medicate the water. YOu could try over counter eyedrops but there is no way to tell for sure if an infection is causing an eye problem.
I understand your frustration but there is no other advice that can be given. The best you can do if you are no going to try your best to get a vet to see this animal is to keep it's environment warm and clean and keep trying to provide live food (worms and such would be a good choice) and hope for the best.
Here is a vet list http://nytts.org/nytts/helpnet.htm#NY
Find your state on it and see if there is someone nearby who may be able to help.
I am not trying to get on your case but don't get on everyone else's case because they offer you the only good and proper advice there is in a situation like this.
In the future no matter how difficult it is to see, please refrain from "saving" baby turtles unless you have access to someone who can assist you with medical problems.
Your heart was in the right place trying to get it away from all those sick turtles in the tank but now you have a sick animal that you are unable to do much for.
This little one my recover on it's own but proper medical help it may not happen and so you have an animal that may very well just sit there and linger for weeks until it dies. I hope this does not happen but in all the time I have done turtle rescue I can say this much -- it does not look promising.
Where are you located? Perhaps I know of a rescue near you that could take the animal and get it the proper medical attention.
Good luck with him.