Attach your Bowden extruder system to 2 of these blocks and mount it anywhere along the Z-axis support threaded rods.
4 x nuts to secure these blocks to the threaded rod.
2 x 20mm M3 screws and nuts to mount the Bowden extruder to these blocks.
Check my "Makes" in my profile for the Bowden extruder model.
Print two of these at 0.2mm 30% infill.