Try taking the measurements and fitting type (flat, philips, hex etc) from another screw and Google it. Worked for me for a tiny sunroof screw I thought would never be available. You might need to ask a jeweller to measure it for you to get accurate dimensions.
I took the top off a Pentax ME Super once, the PCB was soooooo close to where the screws ended, if i put a 2mm longer screw in, it would have done some damage, that's why i posted