I recently blew out one of my tires and since the car lacks a spare I had to have the car towed. I have since replaced the tire and the one on the opposing side of the car, so that they wear evenly. So now i have a semi-used tire that i'd like to convert into a fullsized spare.

Does anyone know where I can get a single cheap wheel to use as a spare?

If I use an 18" tire as a spare and need to fit it on the back(19" in back) will I have any issues with difference in size?