Hmm, I thought I understood what you were looking for - the harness end - but it sounds more like you want the opposite side which would normally be on the socket base? I don't know if GM offers that in a separate part since normally it's a part of the CHMSL / 3rd brake light itself. Are you making some kind of custom piece? You may be better off buying some cheapo Chinese LED 3rd brake light and chopping the connector off.. maybe cheaper that way. Example - here's one for $16.
https://www.ebay.com/itm/Smoke-1994...538565?hash=item3b2e5738c5:g:wFIAAOSwhQpd1jJ7 - the opposite side of the pigtail alone costs more than that from GM / AC Delco!
The confusion on male vs. female - the truck harness portion I would consider the male side, since it has the protruding pins. Only the plastic connector housing would appear female in that case. The CHMSL side has the female (socket) pins.
My original reply had this info for anyone that may be looking for the harness pigtail - GM part # 12102900 or AC Delco PT382; expect to spend at least $25 for this pigtail but that's no shocker as repair pigtails are usually way more expensive than you think they oughta be.
Richard