Chances of finding just a barrel are probably not that good, and if you did find one i doubt it would be cheap. A cheap sporter can be had for $150 or less, and you can sell most of the parts you don't need and get a good chunk of that money back. More work maybe (depends how the barrel comes off, I'm not sure if its pinned or pressed or what...) but probably a lot cheaper and faster to go this route.