The vertical fittings I've seen were made by Mafac for mounting a rear Racer, etc., center-pull brake AND bolted through the bridge from above - to also attach a mudguard (ref.478E).
Weinmann also made one model during the 1970s (# 44.12) but the illustrations I've seen indicate those had a long pivot bolt pre-molded into the alloy piece which straddles the brake bridge - which means that these were really designed for their side-pull brakes - only. [Hmmm. those might work to retro-fit old Campy brakes, too!]
Anyway, I'm looking for the Mafac version. These were a simple alloy piece with a radius carved on the bottom to rest it snug over a standard brake bridge, and bored through to bolt on vertically. It had a threaded side opening for attaching a SHORT 6mm pivot bolt (actually, one of the twin arm mounting pivots fits here perfectly, as well.
If anyone has a spare they would consider selling, please let me know.
Bob Hanson, Albuquerque, New Mexico, USA