Quoted:
Anyone know the exact size of the set screw on the focus lock ring. More important would be where I can get one. Never been able to find one that small. I use a precision screwdriver I filed down and it works but would like to get the actual correct tool. Also do some actually use a type of glue to lock it in place. I had one I actually had to break off to reset the focus lock.

I know most just screw the focus ring all the way up and leave it but I like to set mine the correct way. I have plenty of tools for night vision and this is the one tool I can never find.