They provide enough walnut shell media to fill a tumbler when you purchase one, or at least mine came with some a few weeks back. You can also get it from places which sell ammunition reloading supplies, as it's used to polish reused brass shell casings. I bought a bit on Amazon for a reasonable price, but some suppliers had insane pricing. There's a "guide to tumbling" sticky post, at the top of this section, with a lot of useful info.
Rob, thanks for that lightning quick reply. now by walnut media I am going to assume you do not mean this beautiful walnut media center here, but inn fact mean some kind of ground walnut shells? i could just follow my old man around for a few weeks...
I didn't see walnut in the tumbling media section only the pin and disc shot
Anything round that you can seal and is tough enough to be used as a tumbler, if it's cleaning/polishing you're after. You would need wheels and belts to step down the speed of a motor to something that wouldn't fire your container through the basement wall though. Ultimately you might be best off checking message boards for shooters and rock hounds who are looking to upgrade their tumblers, then pick up some walnut media here or elsewhere.