Summary

Right-angle mounting bracket for 28BYJ-48 (small 5V geared stepper) using M3 hardware. Version 1 has a smaller hole for the shaft, and is simpler to print, without countersunk holes for the M3 screws holding the motor. Version 2 has more shaft clearance for a particular timing belt pulley I'm using, and also makes the front surface flush. I think V2 is better, if your printer can manage the overhang caused by the countersunk holes for the M3 screws. Version 3 adds a side flange for more mounting options. V4 adds a front flange to resist down-tip when pulley belt exits below.
The SCAD files are provided so you can adjust to suit.