Not learning about cryo stuff

I need a small non-feedthrough linear actuator (with say a 1 cm stroke) or rotary stepper motor or just a stupid shutter that operates in a moderate vacuum at cryo temperature. Google is not helping. Guess I have to resort to the old remedy of finding an actual engineer.

(Being sick and having been woken up by rilkekind at 5 AM because, so he claimed, he needed a fingernail clipped might be as much to blame as google.)