There are other brands that likely would be a suitable replacement for Royal Canin, although one of the primary ones is another prescription food - Hill's. Although, a lot of folks on this site will tell you that a wet (canned) food diet of any kind would serve about the same purposes of the prescription foods. It mostly seems to be all about the hydration. It also can depend on why your cat needs these kinds of foods - crystals? If so, what kind? High or low urine PH?