A small linear sled that you can adjust using a twist knob. I made it modular so you can stack it for an XY base.

Might need to print two knobs at a time so that the plastic has time to cool down.

You will need:

2-56 bolt that is about 3/4" long
2-56 nut
JB-Weld or other epoxy

Push the 2-56 nut into the top plate and use a screw driver to push it down until you can see the hole of the plate and nut line up. Push the 2-56 bolt into the twist knob (you might have to use a drill and open the knob hole a bit. Use epoxy to adhere the bolt to the knob. MAKE SURE THE BOLT IS AS STRAIT AS YOU CAN GET IT AS THE EPOXY DRIES! Else it might not go the nut in the top sled.

I tested a lot of these and they are pretty snug.