Thanks Deejay. My solution to the problem runs to the simple, bordering on brutal: see if I can find a disused swimming pool pump in some junk area or whatever, and focus on how to mount it on the mower. I wouldn't do that on a collectable mower, but I have difficulty taking electric lawnmowers seriously as collector's pieces. However your contact would obviously know exactly what the original motor would have been, and that is useful information.

I wonder if it is possible that the whole thing is an engine-driven SB that someone converted to electric?