The kind of tumbler I've seen before seemed like a fairly simple arrangement - some kind of barrel turned by horizontal rollers, similar to a tumble dryer, so that's what I set out to build.
1) electric motor from Grand Am electric window lifter.
2) old PC power supply. This one happens to be a 90W supply.
3) rollers - could be broom handle or any round pole. These are actually mini rolling pins from my wife's craft supplies.
4) various bits of wood to make a frame and base board.
5) 2 inches of garden hose.
6) power switch.
7) screws, coach bolts w/ nuts
8) anti-slip shelf liner
3) Drill + appropriate sized bits
5) Sharp knife
6) Soldering iron (or use crimp-on spade connectors)