Help with missing gas cap parts

[3DdesignsK75S]

I am working on a recently acquired K75S. Long story short, I just ordered a bunch of parts for the fuel system including the new recommended gasket set for cap, however as I wanted to replace the old parts I just realized I am actually missing pieces of the cap.

Any ideas where I could get them from? Checked at MAX where I got the gasket kit, but they don't seem to have it nor anybody else where I looked.
Pls see the attached pic (screen captures from Chris Harris' YouTube) that shows what I am missing.

Thanks in advance

[Inge K.]

You can't buy single parts, beside gaskets (what's left of them, NLA from BMW).
Search a used cap on Ebay, but avoid the very early ones with a pushbutton, they let water through.