Have you tried the Royal Canin kidney diet kibble? They also have canned meat loaf which you could mix in. I warn you it isn't cheap but my dog used to wolf it down!
I didn't like the ingredients list, after having given my dog the best quality holistic organic meat-based food plus home cooked meat dinners for years! But I had to admit I am sure it made a difference to my dog's blood test results two months later. And I also have to admit the food did smell quite good -to my nose!
My dog was diagnosed with early-stage kidney failure....now all dogs are different, and all conditions are different, so do ask your vet's advice....but I have heard that green tripe is usually okay (though I have also heard it smells horrible when it's cooking! -though dogs love it!) Also, my dog was allowed some chicken breast occasionally and a little white fish, and sometimes a scrambled egg for breakfast. I usually included a quarter teaspoon of powdered dried eggshell (for the phosphorus-binder, Calcium Carbonate)
Vegetables of course were no threat, and neither were carbohydrates like potatoes or rice -given of course in small amounts, and not as the main bulk of the meal.
But do ask your vet about those options first.