Jay,
I thought Tijeras got absorbed into Cedar Crest? Our friend. Eric lives on Matterhorn up there.
As for the barrels, it's gonna be a longshot finding some. They didn't make that many 20g guns and finding barrels alone is always a longshot. It's possible it may only take a little while of searching the popular internet sites to find some, but more likely it'll take years or you might never find some.
Keep checking Vintage Sporting Arms, GunsAmerica, Gunbroker, AuctionArms, ebay etc. You might also have to buy a complete gun with a broken stock or worse. Don't pass up dented barrels.