There are several different prescription renal diets available. Most vets carry the Hills k/d, but will special order any of the others for you. Purina NF (dry or canned) Iams Multi-Stage Renal, Royal Canin Low Protein, and at one time Waltham's made a renal prescription diet (not sure if it's still available.) The only OTC low protein/low phosphorus food that I am aware of is Triumph brand Hi-Tor neo diet, but I'm not sure where it can be purchased. When Purina changed their formulation, I called Triumph, and their customer service was quite helpful in regards to DMA analysis and store locators, but I never persued it because my cats transitioned to Royal Canin without incident.
My renal cats were fed Purina NF canned food for years, until Purina changed their formulation. I switched to Royal Canin Low Protein, and they love it. They will also eat Hills k/d occasionally. They didn't care for the Iams/Eukanuba or the Hi-Tor neo diet. It was so long ago when we tried the Waltham's, that I don't even remember if they liked it or not...must be they didn't, because I never re-ordered it. (I had to have my vet call a script in to VetCentric, as they were the only distributor I could find for it.)
If you have any questions about what to ask your vet when ordering food, please feel free to PM me. I also have the phone number for VetCentric, if you want to order from them.