http://slhondaparts.com/browse.asp?M...ViewParts=true

You can buy from there, or use the part number (42200-SM4-J51) to buy elsewhere, like here:

http://www.hondapartsnow.com/genuine...0-SM4-J51.html

I haven't done the rear bearings so I'm not familiar with the design, but looking at replacement parts from normal parts suppliers it appears that the hub is integral with the bearings so the whole piece is replaced. For $137 I would buy genuine rather than save $20 on a generic part, or pull one at a salvage yard.