This compact and inexpensive lead screw is used to move the Z-axis up and down. It is 250mm long with a 4mm lead and 1mm pitch. It comes with a matching nut.

Optional Modification

You can forgo modification, and instead opt for some extra to stick out the bottom. But a full length lead screw will not allow the Z Axis assembly to fit within a filament box. Cut about 10mm off the lead screw, winding up around 225mm. Precision is not required here.