The only things I can suggest is try contacting Rossi. They may have parts for dis-continued guns in the warehouse. They do not make side x side guns anymore.
Also keep an eye on the auction sights, GunBroker.com and GunAuction.com both have parts listings. there are single barrels on GunBroker. It may be possible to fit one in place of the bad barrel
You can sign up on Numrich Gun Parts and put the barrel assembly on a wish list. You will be notified when barrels come in.
The cost of replacing the barrel can be more than the gun is worth, It is a lot of work to remove and then align and solder a new barrel in place, polish and refinish. I doubt it can be done for under $450.
Sorry I don't have any better info for you. It is getting very hard to find parts for a lot of guns, even some that have only been out for 3 or 4 years are hard to get parts for.