HW/Weihrauch HW35 Leather Piston Seal Assembly

I have an older (1970?) HW35 that has been converted to a plastic piston seal. I want to change it back to a leather seal. I have the leather seal on order but I can't find the other parts I need. From pictures, it looks like I would need a plastic cup like part to fit inside the leather seal and a round nut to thread on and hold everything together. I can make the parts but I need the dimensions. Does anyone have any of these lying around that could measure them for me? I assume every time a conversion kit is sold someone has these leftover parts.

Thanks for your help,

Jay