This is an expensive suggestion, but there is a company here in NJ called D'Artagnan, and the meats are all organic or wild.
It is meant for human consumption, but we always share with our (VERY SPOILED) boys, and they have yet to get sick from anything from D'Artagnan. May be worth a try if all other avenues are exhausted. When Mickey was so sick in December and January (he went from 9 pounds to 6 pounds), I fed him organic meat from them for nearly 4 weeks- I personally think it made a huge difference in helping get him healthy again, and I was able to re-introduce (different) prepared foods; he now up to 12.5 pounds of muscle, and to me, that is much more important to me than how much I spent feeding three kitties D'artagnan for 4 weeks.
Nikki, where do you get it? And what kind do you feed? Is that the brand I see at Shoprite?