Or perhaps call Nashbar, they should be able to tell you the size, which is all you need. Once you have that, the Phil site is pretty detailed on which bearings to order for a specific size.

Another good choice for Bearings is NTN Bearings. They are probably nicer than Phil bearings (more expensive though). The good thing about NTN though is that you can likely find them in most major cities in North America. Again, all you need is the size of your Nashbar bearings.