Thanks all.
I have talked to Don, and he quoted me 10$ for a red dot, which is perfect for a replacement, but can be a bit steep if I want a bunch of them for experimentation of painting.
I am not after black dotsince they have reached a status and rarity that apparently makes them very expensive, and I really couldn't care lesss to actually have "Leica" written there, whatever the background is.
Actally, I would love to have a simple black metal, blank adhesive cover.
Maybe an idea for some Chinese entrepreneur 😉
EDIT
Gabor,
Thanks for the idea, but I've seen some pretty ugly M6s with the remains of the glue from tape, and it wasn't a pretty sight...