I have the same spool holder on my printer. My problem is that the last batch of PLA I ordered (off of EBay) the spools were wider than the one that came with my printer and the holder does not fit the wider spool. I am going to have to either look on Thingiverse, design my own or something. In the interim I just took the PLA off the wider smaller diameter spool and rewound it on the spool mine came with but that is a real pain in the butt. I think I am going to incorporate your bearing idea as I think I have a couple old bearings in the garage from another project that I could use. I will post up my solution when I come up with it.