So the issue is finding a CPL that is 3mm thick AND the right diameter of the glass. Also one needs to be able to get the existing CPL glass out of the holder and it's held in by a snap ring that will require some very thin pointed tools remove.
Anyone done this before?
provided that you have found the correct thickness, trimming it to fit is easy. this is what we do when replacing watch crystals. the glass is fit to a table and the edges are ground to fit. its a delicate and tedious process involving plenty of water. send it to a watchmaker and it should be an easy task for him to find somebody who will do that for you. alternatively, it should be easier to modify the holder itself.
removal of the retention ring involves a screw driver. if you dont care for the filter holder then you can saw a slot to help you flick off the retention ring. it can be a delicate process depending on the type of holder. brass ones can be a pain specially the thin ones. i tried doing this before on a lens with a stuck filter (dropped, ding.)
