Renal diets for a cat with multiple food allergies?

This stumps vets a bit, too, though food allergies are hardly rare.

My cat will be 20 at the end of September and has recently shown some signs of moving towards early stage 2 - depending on how people veiw Antech's tests and ranges.

He started out, when he was a kitten, with a chicken allergy that progressed into all poultry, and eventually picked up a rabbit allergy due to trying to avoid all the poultry foods... As a kitten even hydrolyzed chicken was...awful. Age and those allergies have progressed to some mild IBD - he's maintained on a low dose of budsonide, digestive enzymes, and fiber added to his wet food.

The problem being most renal diets are poultry or at least contain chicken fat. He isn't too keen on home cooked foods, but otherwise happily eats wet beef, lamb, and fish. Pork bloats him up with stinky painful gas. He still nibbles some dry and drinks plenty.

Has anyone found a beef, lamb, fish, or another novel protein kidney diet with no chicken fat or dried egg? Available in the US.

I know this is a complex request, but also know people can be super resourceful and someone has probably been stuck with a similar food issue.