I know that catsailor sells complete cat trax and some parts but I figured out a way to fix old cracked roleez wheels used in a lot of the trax (and probably works for other types as well). The set I got were old and one of the wheels had cracked and this let air out despite trying all sorts of glues and tire-sealant. I tried one last effort- I drilled a hole in the tire, let as much air out as possible and squirted in 2 cans of expanding foam insulation/sealant (from hardware store). It works... and beats the 100$ replacement cost. HOWEVER, I encourage everyone to support catsailor