Frankfort arsenal on amazon.ca is pretty cheap. I spent the better part of a day screwing around trying to rig up a vibrating tumbler, I also used an old serpentine belt from my truck to run a 5 gallon bucket using my drill press for power, and the cheap Frankfort arsenal one I bought does a way better job, in less time. I did pick up a 12 vdc gear reduction motor from princess auto for $10 to try building a tumbler with, but haven't bothered yet. I might still use it to build a rotary with a bucket some day.
Kristian