There is a major distinction here. The "plasticky" tumblers are
available from toy stores as children's toys and most certainly are
trash. However, most any reputable gem and mineral store will carry
the professional grade tumblers. The most common brand is Loretone.
They come in different sizes and the price increases with size. I
would definitely buy the drum but making the motor housing would be a
good project. Another money saving tip: the good brands are nearly
indestructible, so a used one is a good buy. Also, the drums wear out
more frequently than the motors, so if you wanted to have one sure of
not leaking, I would try to find a used motor unit with a new drum.
Another thought when it comes to size: the silicon carbide abrasive is
expensive. My large tumbler, a 12 pounder, uses a pound of abrasive
per step and costs almost $30 per load to fill with the proper
material.
Hope this info is useful.