Parameterized re-implementation of Antscran's bearing. I made this so I could print a bearing for other sizes of rod, but you can also experiment with tweaking the clearance, size, and number of PTFE tubes.
Attached stl, and default settings on the jscad file are a near exact clone of the original LM8LUU with 8.4mm ID. Try tweaking the settings to fit your needs. I added the ability to spiral the slots for the PTFE hoping this would add some support.