I need one rim and tire for my tiller and would like to know where I can get one cheap.
The word--CHEAP--is not in the Troy-bilt dictionary!
But, you might find somebody who will sell you wheels.
Maybe you could make a set of wheels, using some steel tubing, and wheels from something else. Yankee Ingenuity comes into view here.
I get a lot of Troy-Bilt parts from custompartsinc.com.