Remix of www.thingiverse.com/thing:3063886 Extended the mount arm by 10mm, added a shoulder for the 608 bearing, created a bearing retainer that captures the filament, created a 2 piece press on pulley for the bearing. Requires a 608 bearing and an M3x10 bolt for the bearing retainer. See below for important print information.
If printed in PLA at 100% everything should work. For ABS I had to print the mount arm and bearing retainer at 101.5% and the pulley at 100.3%, to accomodate shrinkage. I suggest printing one pulley half and a mount arm that is sunk into the slicers print bed so it only prints the bearing shoulder and spindle, to assure the parts fit correctly. These values were set in Cura.