Clown gobies will do that - kind of go white at night. (At least mine does.)
I wouldn't worry about it not eating after only a few hours. To be honest, when I bring home a new fish and put it into the quarantine, I don't feed at all for at least 24 hours. That way, he can devote all his energy to getting acclimated, and not trying to digest food.
But to answer your original question, most of the LFS in my area (the good ones!) have it. I'd call around.