Cedar Rapids Brewing Society

I was just at Marion Iron, and they have a 50L keg in good shape. It's got some non-Sankey hookup, but would make a nice kettle or other brewing vessel if you cut off the top. Google tells me that 50L is 13.2 gallons, so a little smaller than 1/2 barrel (=15.5 gallons). It looks to be about the same diameter, but a little shorter. My experience has been ~$40 for a 1/2 bbl keg, so expect that or maybe a little less for a legal keg.

I swung up there to take a look at their keg offerings, got a great looking AB keg. Its in perfect shape, they charged me $40 even for it. They had 4 other banged up kegs, but all usable if you're not concerned with aesthetics.