No plans, I made one from a 5 gallon pail with a snap down 'o' ringed lid, some angle iron, steel axles (bar stock), pulleys, belt and motor from Grainger .
A little welding and an afternoon and I have a nice wet tunbler that will do 1000 308 cases at a crack (you need a bit more than one bag of pins however).
Looking back, if I could have gotten a 2.5 gallon it would have been easier to handle.