[footfootfoot]

you could pick up an inexpensive electric drill, mount it to a wooden base, and chuck a bolt into it that would hold the disk. Most VS drills have a trigger lock. You could also plug the drill into a dimmer and use that to adjust your speed.

Depending on how tight you bolted the disk, that connection could act as a sort of clutch.

Any small, variable speed motor would do. I'm sure you cold pick up a turntable at goodwill and use that. Belt drive would allow for the disk to slip and would allow you to gear down or up.