Summicron 50mm f2 rigid - aperture ring screw missing

[npeters]

Hi - I have a Summicron 50mm f2 chrome rigid, s/n 1401***, so I guess it's from about 1958 or so .

I have just noticed that there is a tiny screw (1 of 3) missing from the aperture ring. Can anyone advise me where to get a replacement - I live in Australia. Perhaps a part number might help me if anyone knows what these are.

Alternately, can anyone donate me one? It looks tiny - < 1mm diameter, and I believe it fixes the aperture scale in the correct registration (along with the other 2 screws that are still there).

Cheers, Norm