Not long ago I've read about sort of plastic linear bearings, igus. Though it is interesting, it doesn't solve my problem at this minute and I need a solution now.
I've started looking into other solutions on thingiverse and eventually decided to try my own design
|My Linear Bearing|
The design is for grease, there is a spiral inside it with holes that go from top to bottom, so when too much grease accumulates on one side, it will be pushed back to the other.
I've used white ABS with 0.2mm nozzle and printed them very slow so the bad bearing won't shake too much. I've read that if the bearing are too tight, you can use acetone on the rods to loosen them up.