every now and then you'll see one on craigslist but they don't last long because the growers and the brewers want 'em.

most places just trade 'em out so you don't really own a particular tank. Way to Grow charges $10 for trade-outs on #20's, which is pretty reasonable. All that I've seen on the #20 size have collars.

the other good thing about them is, they hold a good bit of their value as they are always in demand.