If you live in a metropolitan area, you can just go to a supply house and pick up some... I did that for my ancient OS 46 SF-ABC, paid next to nothing, they fit perfectly, and had them instantly.

Edit: just checked the popular web site selling bearings, and holy cow... $30? I'd have to check to be sure, but I think I paid a fraction of that for my replacements at the local supply house... maybe they aren't equal, but thy seem to work.