Looking for a premium dog food following allergy testing. Any ideas?

My shar pei has skin and ear issues/infections with most foods. He has been on Hills Prescription Diet, Z/D ultra hypoallergenic for several years, and it has done wonders for him. It is expensive, and you have to get it at a vets office, but I find it worth it, especially when you consider the $ saved by not having to have infections treated.