I searched for a mount for my extruder motor for a long time.
I finally decided to just model something simple.

It is a super generic design that will fit any motor and could be adapted to fit almost any vertical mounting surface.
The motor is strapped down using zipties, and seems to hold really well.

I am going to make a variation to rotate the stepper 45 degrees to give a bit more flexibility to bowden setups.

Included the 123d design file as well so others can modify it.