Need help finding screws - Vivitar 28mm f2 MD to EOS convert

[sammo]

Hi,

I am stuck in a middle of a little project in repairing and modifying a Vivitar 28mm f2 to EOS mount.
The blades were very oily and stuck so I had to clear them, I also cleaned and relubricated all the mecanisms.
Removal of the old mount is easy a M42 to EOS adapter fits nicely, infitity focus is easy to adjust.
...but...
The screws that hold the original mount to the lens are quite short, and also the threads in the lens start just some millimeter already in the holes, so I found the screws too short to attach the M42 EOS adapter to the lens. To do it with original screws would need a irreversible modification or a new machined part on the back, so I figure that to try to get just longer screws would be the most elegant solution.

The original screws have a thread of 1.66mm diameter x 0.34mm pitch, lenght 5mm. I would need at least 6mm...
I found standard dimensions of metric threads to be 1.6x0.35. I this in the same error range as what I need?

I would be glad if somebody has any experience with this, especially about where to get these specialized screws.

Samo