Thanks Bikemad.
I found this site also that seems to offer it...
www.surplustraders.net...but I'd still love to know the original manufacturer to see if I can get it at 'more common' electronics distributors like Digi-Key, Mouser, etc. I know the connectors mounted on the GM motor controllers are the Molex Mini-Fit series, but this one seems pretty rare. Or maybe it's a non-proprietary design and there are several manufacturers.
Thanks again