As Surpmil says above, while there are about 6 versions of the TOP part of the clicker, varying from 2 MOA, 50 yard Mk1 type to te full radius Mk3 1 MoA versions, there are 4 variations of the Mk4 version......., probably plus some! Full toothed radius, partially radiussed and so on..... Then there's the raised or lower centre..... See what I mean.
We had drawers full of Mk1 types at one time - and I think that I still have a zillion sets somewhere that should be readily convertible. Getting a set made ........ The material has to be exact. Too hard and it will destroy the clicker plunger within weeks. Too soft and the hard plunger will destroy the nice new clicker plate.
Be advised that while the parts list identified the Mk1 range and deflection drum component parts. It was a list of PARTS and not a list of AVAILABLE parts. I NEVER saw Mk1 (or 2 come to that.....) drum parts separately - except the screws and lock nuts of course