I wonder what the standard screw threads in a Vibroplex are, bearing in mind its genesis of 100 years ago?
I imagine that it wouldn't be BA, as this was a Britland standard.
I've sorted through the junk box for this project and have located a gert lump of black-rolled steel for the base, and quite a few offcuts of brass for all the bits.
What metal is the Vibroplex pendulum made from? I've got a piece of thin brass which might do the job.