Cat with LYMPHANGIECTASIA

My year old cat, Mittens, has lymphangiectasia (very rare in cats). He is on prednisone at the moment, but I am unsure what to feed him. I know he needs a low fat, high protein, grain free diet, but is there one that works? I know switching him to the raw food diet might be best, but I want to know what type of raw diet as well. I would really appreciate any help. He also has haemobartonella as a result of this lymphangiectasia, so we are hoping the medication and new, strict diet will be the best way forward. I appreciate your thoughts on this.