Inspired by 3d-printers using braided-wire "Spectra line" instead of timing belts.
The wire is tied to the pulley at the middle, which means it is not friction which holds the position. This allows using basically any non-stretchy wire for driving a linear system.
Idler discs are desiged for snapping onto a 608 bearing. May need to scale it up/down a little bit according to your specific 3d-printer.
Pulley designed for 5mm motor axel with flat. Can be adjusted in the included FreeCAD source.