They are out of production. If you can find them, extra
connectors have identical bodies for the male and female
side. So you can stick a pin and a receptacle in the same
plastic body. If you take a cue from the SAE folks and
put a receptacle on the hot wire coming from the battery, and a pin
to the ground wire, you get a polarized plug. Unfortunately
for polarization, Later Widder products were manufactured with
rubber-molded connectors, which cannot be mixed and matched in this
way.