Parametric stepper motor mount bracket in U-shape.

This is a fully parametric design; the STL is only one example of how it looks. You can print it if it fits your size requirements (NEMA17 stepper motor, 40 mm long, M3 bolts for wall mounting). Otherwise, open the source code in CadQuery (links below), adapt the measures, generate your own adapted STL, and print that.

The CAD model was made using CadQuery, an open source CAD software similar to OpenSCAD (but much more powerful). The latest version of this design's source code can always be found in my Github repository.