Print two.
Add an m6 nut to each.
Cut a piece of 20mm conduit to length - I used PVC. Steel may work for increased strength.
Insert prints into ends of conduit.
Screw a suitable length of m6 threaded rod through and tighten.
I found a couple of coats of “chlorinated rubber” paint on the ball made these as “grippy” as the commercial rubber-coated mounts.
The author marked this model as their own original creation.