Just looked thru my parts books.... these upper have a 6006 bearing, which is quite the oddball bearing, these phazers have 3 different sizes to them, 6005 in the front lowers, 6004 in the rear lowers, and 6006 in the uppers.... i cannot find any listing for a 6006 bearing... looks like you may be stuck ordering stock!!!... try port yamaha, they seem to have the best prices....
I just had these whells off last night... and the shaft is designed for that 6006 bearing... not alot of room for another size....