Finding a TRANSFER SWITCH is one thing but finding one that will fit in the same spot as your original transfer switch may be the problem area.
You might not want to rule out to having one installed outside the WFCO Power Distribution Panel and run wires from the external transfer switch box location to where they need to go. All it needs is to be installed in an approved electrical box with removal lid.
Probably not much fun in CONWAY AR but this is not all that far from JACKSONVILLE-NORTH LITTLE ROCK where you might find some RV places. LRAFB is located at Jacksonville which is probably home for many RV units.
The transfer switch itself is nothing more than a 30A or 50A multi-pole electrical 2-position 120VAC contactor. Any Electrical supply place would have something that would work. Folks wire-in Generators to their household all the time.
A good Electrical Repair Shop should be able to get you back on the road with something...
Also don't rule out MARINE BOAT places. BLUE SEA sells similar transfer switches... Arkansas is known for its many lakes for fishing. Lots of Lakes 30 minutes from each each means lots of boats similar equipped like your motorhome..
I know we are not much help for you - sorry you are in a stranded mode.
Roy Ken