Use this to make a model for a bushing/housing all in one that snaps in place around the guide rods. This does fully constrain 360 degrees around the rod.
I wanted this so I could take off my carriages without removing the guide rods.
The bushing is not a circle, it is an octagon. This helps prevent binding in my testing and observations as I believe there is less surface area contacting the rod, while still keeping the rod constrained.
I had better results (tighter tolerance with less friction) by using thin 8 mm bushings over the convention of using 24 mm bushings. I don't think having longer bushings helps much for that matter when multiple bushings are being used. YMMV, but I'm really happy with their performance.
Also, a good first layer is important for the tolerance, I added a bit of a chamfer to make my life easier here but it will still come in to play.
.stl is what worked well for me, bushing diameter of 8.05, length of 8mm. Mounts with 2 holes instead of 4. Pictures for reference.
Parametric .scad file provided to modify bushing diameter, length, etc.
You will probably have to do some post print processing, I used the sharp edges of my y rod to cut off any minor inaccuracies in the surface for example just by sliding it through the end of the rod a few times. You can slide it quickly on the rod a bit too to loosen them further if needed. Then I clipped it on to the x rod for my x-carriage.