I bought mine from aimsurplus with free shipping, I had been wanting them for awhile, but they were always sold out. I got lucky and looked when they had some in stock and placed an order.
One of these. MD Arms Saiga 12 20 round drum. Will probably add some more Tapco 7.62 mags to the list, I've never had an issue using them and they're nice and cheap. Maybe a few Surefire S12 mags as well.