I hope you have the stud bracket (not sure if this is the name). It is for item no# 39-187 The flat plate it has 2 holes on the left & right. The original is missing.
Bob from SWISCO responded:
August 26, 2020
We don't have an exact match for this bracket, but I'm wondering if you could just use the 39-548 and 39-549. These are flat like yours. See if they could work.