Help finding square ring mandrel

I’ve been looking for a particular ring mandrel for years now and
can’t seem to find it. If anybody has any idea where to look, I would
appreciate the help. It is a square ring mandrel with rounded
corners. Most suppliers have italian quadrillion/cushion
shape/rounded square; square with hard edges; or square with cut
corners, none of which are what I am looking for.

All four sides are perfectly flat, but the corners are rounded not
chamfered. My mother bought this mandrel 10 years ago or more, we
need a second one, but I haven’t been able to find it on
Rio/Stuller/O. F. or any other online source. There are no markings
on the one we have so I have no way to trace it.

Does anyone know how I can get my hands on one of these? Or if there
are any suggestions for a machinist that can make me another one?