My Prusa i3v kit from MakerFarm came with a spool holder made from laser cut wood. It works well enough holding the spool above the print, but sitting on the edge of a wood piece didn't allow the spool to turn smoothly. Occasionally the filament would tighten up, and then the spool would jerk. It was also rubbing plastic away from the inside of the spool. I made this simple little part to print and clip onto the wood allowing the spool to turn more smoothly. It's not a wheel bearing, but it's super easy to make and has made a marked improvement for me.
Simply print and clip onto the spool holder as shown in the pictures.