This is the housing I designed to mount a stepper motor to use as a small generator for use with the water wheel I posted earlier.
There are plates to attach to each side to seal it. Mouse coloured cube is the stepper motor. Light blue is a coupling to join the motor shaft to an M8 allthread rod. Darker blue are a couple of nuts to transfer axial load to a 608 (skateboard) bearing in the bottom of the housing. 3d printable of course.