I found this on craigslist. Figured I'd share it because they are hard to find. http://ventura.craigslist.org/boa/4194202339.html
Also I have one old cat trax wheel that came with my trax it is the wheel on the left that is on the axle. It is the old style wheel. I know the new wheels are expensive. I don't know if this is trash or something some one would like. Let me know if you are interested. It is not new by any means. I am pretty sure it holds air. But I will confirm!
1981 Hobie 16 cat fever
1981 Hobie 16 double plum