Roller Assembly for upper track of mirrored sliding closet doors

The adjustment screw tab has snapped off the roller assembly for the upper mounted track for mirrored sliding closet doors. The brand of door is Texas Mirror, Inc. These doors are about 35 years old. The rollers are Acme brand, US Pat. 3750337. The roller bracket has 4021 stamped in it, and the main bracket has 4050 stamped in it. It attaches to the doors by bending tabs into slits in the door frame edge. the adjustment screw is missing due to the tab breaking off.