Altrex Duo-Sync for Nikon. Marked "FG" but also works with FE, FE2, FM, FM2, FA. As you can see, 3 pins for sync plus the center power contact. Bottom of the "remote" end has a 1/4x20 socket for mounting.
$13 plus shipping (can ship First Class pretty cheap).
$13 plus shipping (can ship First Class pretty cheap).