It's a modernized version of a Stevens Favorite, so, while I have not actually seen barrels for it listed, they are not hard to make work.
From my perspective, the 'hard' part, is making and fitting a forend to whatever random barrel you manage to come up with, if you do not buy a barrel blank with suitably straight sides to it.
Got access to a metal lathe? With some care, you can shape the breech end of a take-off barrel to fit the action, without disturbing the chamber, so you can skip the need for a chamber reamer.
Another possible source, is the used gun parts dealers at various gun shows. Those guns have been around for 20 or more years, and there may have been some that have been broken for parts.