The barrel "tub" is everyday kitchenware food container. In this case, a 6" diameter Rubbermaid "Seal'n Saver" #5152 food container. This is a "premium" brand (will cost a few extra $$$), but better suited than the cheap, flimsy ones.
It fit the bill for me in 3 ways:
- it was the right size to fit my tanks (electrolyte and chromate)
- it seemed about the right shape & depth to provide good tumbling action
- it's made of thick, sturdy plastic, reinforced in the right places
Other parts are everyday PVC pipe.