Are you thinking of another than the Recomar? I have three, and I'm going to feel awfully stupid when I get home tonight if I find they have bayonet lens mounts (in fact, I was just fondling them all this morning). Nor does the manual Picture taking with the Kodak Recomar Nos. 18 and 33 (available from the Butkiss site) mention that. It does mention suppementary lenses to acheive 18 cm, 23 cm, and 11cm wide (for the 9x12). I haven't seen them, but have found series VI supplementary lenses for long, wide, and close-up work. As an aside, the Recomar 18 would be a better fit for the OP, since it is a 6x9. I have seen it fitted with a RF, as are two of the Recomar 33s that I have.
I forget now the other plate folding cameras that had interchangable lenses other than the Bee Bee (also a German made camera imported to the US as the Bee Bee). I think both the 9x12 and the 6x9 had two lenses each besides the normal lens. I check ebay from time to time but have yet to find one. The Bee Bee lenses did not bayonet in, but fit into curved flanges top and bottom. The top one had a wire spring to help hold the lens in place, as well as a tabbed wheel on top to lock the lens in.
A 6x9 plate folder might be small enough for the OP, but adding an auxillery RF would increase its size some. Then, unless you can find a roll film holder, you need to use cut film.