Replacement screws for 12mm UW Heliar rear mount

[ncc1701]

After close inspection of this lens a friend gave me, I noticed the four screws at the rear of the mount have a raised round cap, which keeps m-mount adapter from screwing all the way in, thus keeping the distance scale at 90 degrees and likely effecting focus. I have adjusted the mount at first by shifting those 3 screws to either direction before noticing the raised round heads. After seeing other photos on the net, it seems the proper screws have a flat head and must have been swapped out by the previous owner.

How would I go about finding these 4 correct flat screws?

Also can anyone else confirm these screws are indeed flat.

Thanks all!