it might end up being cheaper to just buy a new gun with the barrel on them
finding used shotguns isn't that hard in MOST times, , right now things might be a little harder, but I am sure it can be done if you look
https://www.gunpartscorp.com/categor...barrels-ith-37

https://www.gunpartscorp.com/categor...barrels-ith-37

http://corsonsbarrels.com/

http://shotgunbarrelsandstocks.com/

http://www.gun-parts.com/barrels/

if not new barrel makers like Hastings, and others should carry the barrels you want,
jjust have to look a LITTLE
but again, at prices, close to what a whole new used shotgun will run you?