So you're looking for the mounting plate, which attaches to the bumper and runs horizontally straight back and then does a 90º turn straight down at the rear of the fog light bucket? I should have some in my storage, I have a couple of trashed spoilers in there.
1991 RRC 4.2, R380, LT230, TrueTrac, Detroit, sliders, 33s, blahblahblah....
1994 RRC LWB
1994 RRC SWB
1995 RRC LWB 25th Anniversary Edition
1995 D90 project