I have 3D printed a focus motor attachment & coupler for my C8.
I've shared a photo of my setup before here, I guess you can find it there.
What I like is that it still has a (big!) handwheel.
Would you like to have the design?
It uses a direct drive very flat Nema 17 stepper motor and the SilentStepper drivers (TMC2130) on a breadboard still.
Works flawlessly and runs absolutely smooth. I have attached a temp sensor and configured it to play well with the Moonlite protocol.