I've also got a Grandpa Bear sitting in my shop and we have a small high efficient, air tight stove that I'd been swapping out for the Papa Bear in the Spring and Fall but that's kinda of a pain even though it puts out a lot of heat from a little bit of dry wood. Uninstalling and reinstalling wood stoves twice a year is a pain. If we had more room, I'd have the little air tight sitting next to the Papa Bear and just alternate between them.
Would something like a clay casserole (a Romertopf) or even one of those Coleman camp ovens work on top of there?