The place for small amounts of assorted tumbling media is http://www.eastwood.com/
they have all flavors of the media. Harbor frieght's vibor tombler is made by the same company that supplies them to anybody that wants to put their name on them. They also have a one and two barrel( quart paint can sizes) rubber cans these are the same ones that are sold as the kits for Christmass by most stores at higher prices. One hint from somebody that tumble stones in the past. Depending on what you put in the can for a soap/lube make sure if you are using quartor gallon paint cans or any can with a postive seal. That you stop and open the cans every 24 Hours to relive the pressure. Forgot in my youth and a can poped, what a mess to clean up.
The cement mixer is a good idea if you have small electric driven one around.
have used one to mix large batches of custom parrot seed, assorted beads to bag,
Been there, probably broke it, doing that!
I am not a lawyer, and never played one on TV!
All the usual and standard disclaimers apply. Do not try this at home, use only as directed, No warranties express or implied, for the intended use or the suggested uses, Wear safety glasses, closed course, professionals only