I got these from LMC:
http://www.lmctruck.com/icatalog/cc/full.aspx?Page=22
I have no complaints. The wheels are big enough that they roll easily on my broom swept concrete floor. Right now that are under my '66 1 ton dually and I can roll it around the shop myself. The hardest part is changing directions, but once you get all of the wheels on the dollies pointed in the same direction you are good to go.