NSD sphere for gun or plunger 1.0.0

Does anyone have a 3d file to create the seat the plunger/weapon stalk spheres rotate in within the body of fibreglass shoulders?

i have a donated fibreglass shoulders for our Renegade and the fixed/captive seat is damaged on one side and the seat that clamps via multiple bolts (a mirror image) is lost to the stars 

I made a sort of duplicate using polyester resin and a sector out of a 4" diameter vending half sphere as the bearing surface but it is tatty and not really what I need........... 

The wooden scalloped out clamping cup pairs will pull the pivot point inboard quite a bit if i don't break out the existing seat on one side, i might have to resort to this 

A flat backed 3d print in ABD with tabs for the clamping bolts would be great

My CAD skills are zero else I could turn all the diameters and truncated spheres in my mind into something tangeable!

Many thanks 

Dr B 

Photo left looks a bit like a dalek eye!