So, as a stopgap I acquired two Horseshoe Cincinnati 1Ks to fill out the rack.
Still looking for 2, 12, 22 or 42 JD1KSes though!
Notes: The Cinci 1Ks are 43mm and have the identical base color. The spot pattern and colors are different, but not so different that they can’t blend reasonably with the Jacks. Not ideal, but the best I could do considering the paucity of 1K Secondaries out there.