Fisher fan add-on

Have you removed the plate to see what's under it? If that's a hole cut under the flue outlet, perhaps there is a second hole under the plate where someone installed a water coil or black iron pipe loop? (natural water movement from being heated above the flames rises out the top hole, and the lower hole becomes the inlet to reheat the circulating water) In any case, that galvanized electical cover plate should be 1/4 inch steel plate. The back of the stove can reach temperatures to burn off the zinc coating, creating toxic smoke / fumes.

A fan would require a shield across the back with a hole cut through it to pull hot air from between the stove wall and shield. A long cage type fan across the bottom moving air upward between a rear shield and stove back is the best add on type blower. The rear shield is made a couple inches higher than the stove top and curled towards the front to blow the already heated air forward across the stove top.