I recently came across a site that sold industrial ball-bearings. There was a whole section for yoyo ball bearings. Some are for yomega, some are for duncans, some are for yyjs, etc. Most of them are in 10 packs, but I found a 1-paack that supposedly is a size C bearing (.250 x .500 x .187) that fits yyjs and the like.
The link to that: http://www.vxb.com/page/bearings/PROD/YoYo/R188ZZ-1
There is also some yomega ball bearings (Can fit my Maverick) that supposedly spins 71,000 RPM. Is that good? (It sounds incredible!) http://www.vxb.com/page/bearings/PROD/YoYo/Kit179
Have any of you guys tried these bearings? They seem O.K., but I’d like to see your opinions.