I used the 619/8 bearings. 608 bearings have 8mm inner diameter, 22mm outer diameter and 7mm width. 619/8 have 8mm inner diameter, 19mm outer diameter and 6mm width. I put a washer aside each bearing to correct the width.
For the outside i made some rings of polyurethane and pushed them over the bearings. Or you can use some strong rubber tape.
I know, a bit unsatisfying these answer. But i wanted some smooth running bearings and ended making them by myself. It's like the dual extruder head i'm making.