Source needed for microphone positioners (linear slides)

[Aerosc]

I'm starting a new project to map the acoustic pressure field in a rectangular duct using microphones with 'coffee stirrer'-type probe tips. I need to set up a mechanism to allow me to control the depth of the probe tip in the duct and thought some type of linear actuator would be appropriate. Can anyone supply a source for such actuators? I'd like them to be electric and provide position feedback.

Thanks in advance