I got some electric motors from RB's in WA that had them for 'topless' rods [6 or 12V] of the type that mount on top of the windshield frame - fit right in the space of my 46, and the covers still went on, put a toggle sw in an original hole - they accepted the stock style arm and blade and worked as good as the vacuum ones -
looked like the ones here by Newport Engineering , tho this site doesn't list pre47 application
Bill