The wheels are actually not that hard to find. Rich and I both used idler wheels we found at Surpluss Center,
http://surpluscenter.com/
For my drive wheels I bought them from Rob at Beamont Metal Works, the maker of the KMG Grinder.
http://beaumontmetalworks.com/ If you click on Wheels and Components you will find all you need. I have also bought pillow block bearings from him as well.
Good luck with it