Just look for 1/4 inch ball bearings. Don't put BB in your search terms. You can get them from a local bearing supplier to industry in your local area in your area very cheap.
Don't fill it slam full with loose bearings either, then the bearings won't sit properly in the races. You need one or two bearings less than what you think is full. Even if the race was 66% full with bearings, then that'd be plenty.
Last edited by Iride01; 03-17-22 at 08:48 AM.