This older Celestron focuser (#94144) for refractors works fine and allows for focusing without causing image jitters. Uses 2 AA batteries; battery door loose; I've simply taped it on with black electrical tape.
Not the "latest thing," but a nice accessory for moderate-level 'scopes.
Look at your focuser mechanism for the screws which hold this gizmo in place.
$22.00 shipped CONUS. PayPal or MO.