[Tristan Lall]

Are you hoping for a self-contained solution (i.e. all those functions in a single unit), or would components be fine?

Also, what's the orientation and loading of the linear actuator? Do acceleration (and deceleration) matter? How variable does the speed need to be (fine or coarse control; large range or small range)? Any environmental issues (oil, contaminants, etc.)? Do you need absolute position feedback or relative, and do you need it in human-readable form or electronic? Is this for an FRC application?

I've used leadscrew-driven slide stages from Velmex before. They were quite nice, because they could support heavy loads travelling horizontally, but I'm not sure how fast they could reliably be driven. I believe they had ones with motors attached; we only used the hand-cranked ones. Some had graduations and vernier dials; maybe they have versions with encoders.