There is also the build your own approach. I would look for most any American made
TEFC totaly enclosed fan cooled motor. Baldor motors are the best, but there are a lot of well made tefc motors that are up to the task. I would scour Craigs List and check with motor rewinding shops to find an appropriate motor. Open frame motors, do not fare well in a dirty shop.
I would recommend a belt guard, and placing the switch in a better location, it you decide to do something similar.
Here is my set up, for a little food for thought. It offers a good deal of speed and wheel size variability. Just tossing out ideas.
Charlie