Harness connector help - 66 C10/C20

[JPTL]

I'm replacing the tail light harness from LMC that has a female 3 wire plug connector (pic 1). This plugs into the intermediate harness that runs along the inside of the left frame rail from the firewall.
The intermediate harness must have had a 3 wire male plug connector (pic 2), but that connector is long gone.
I don't want to replace the intermediate harness since the original is in decent shape - except for the missing connector.
Any idea where I can get a male 3 wire connector like the one pictured (pic 2)?