I got my parts from Roger Raagatz, Pardeeville, WI. 608-429-9267. When I was searching for parts, I spoke to someone that had parted out a RO 20, but don't recall who that was. List of contacts is below.
I would not recommend welding a fire pot, rather find a different one in good shape.
Madison Stove Works Madison WI 608-516-0890 Rich Gloe stove restoration, parts and I believe rolls cylinders
Dean Hron Cresco IA 563-547-5521 or cell 319-240-9425 stove parts and rolls cylinders
Brian Spandel Long Prairie MN 320-594-2799 rolls cylinders
Hardscrabble Antiques Hazelgreen WI 608-884-2525 Kyle Fredericks stoves, stove parts and restoration
Kickapoo Trading Post Readstown WI 608-629-5088 stoves and parts
Fox Hollow Antiques Gales Creek OR 503-357-8710 Gary Davis stoves, stove parts and casts stove parts. Website: http://www.roundoakman.com
Several people I know have got new parts from him
Tomahawk Foundry Rice Lake WI 715-234-4498 Website: http://www.tomahawkfoundry.com
Send them a part for a pattern and they will reproduce it.