Caliper adjuster for Shimano 600 brakes I have a pair of 1980s Shimano 600 brake calipers that look very similar to this


From https://www.picclickimg.com/d/w1600/pict/253060189019_/SHIMANO-600-BR-6207-etriers-de-frein-brake-caliper.jpg

Sadly the cable barrel adjusters have gone missing. I thought they'd be easy to find on ebay but I'm not sure exactly what I'm looking for and some of them seem to be selling for several times what the calipers are worth!

The hole in the caliper arm that should hold the adjuster is not threaded internally. However, it is partly flat so the hole is not perfectly round. Could anyone suggest where I could get such a part cheaply, or a formal name for it that I could use to help me search? I'm not bothered whether it looks retro or not.

Looking at pictures on line, it looks as though sometimes there is a nut above and below the threaded barrel adjuster and sometimes only above it. In the latter case is the adjuster held in place only by the pressure of the cable outer above it?
The part is called simply brake adjuster or brake adjusting barrel or "bremszugeinsteller" in the promised land of affordable mail order. It is indeed held in place only by pressure from cable and is easily lost when the cable is removed. In the picture the nut is put on wrong side to hold the adjuster in place without cable, I have never seen a second nut like on the right before.