Welding is an idea; the lands & grooves could be left untouched by putting a copper rod down the barrel and then TIG/MIG welding it (the weld won't adhere to copper). But then you need to dress it and re-blue it...
A new barrel is probably the best idea, if you don't care about matching. I've had the thought that 'pulls' [removed used barrels] should be right at $100, but I paid more than that for one a few weeks back and looking at GB/eBay I'm seeing up to $200...
