I see many people asking about these, and I have come accross something like this. It isn't an actuator as such, but you could achieve the same results.
here
You will need a stepper motor controller for it, but thats no big deal.
The other option to DIY is to use lead screws, and a dc motor with a control board that has a couple of limit switch inputs. Should be able to do something on the cheap that way.
Thought it might be of interest.

And here, this one has the controller board I mentioned.
here