Circlip pliers the L shape work best they get more torque to turn the screw.
If you want to replace the screw once you have it out then look for an M3 screw 5 or 6mm long. You’ll need a washer to fit as the M3 screw head is too small to bridge the hole in the scales. The M3 screw takes a 2mm hex key. Total cost about 50p - phosphor-bronze washer was the only one I had that fitted otherwise it would have cost about 5p.
Problem solved.
If you are in the U.K. I can recommend Kays Fasteners e-bay store quick service and free delivery on most items.