a NTN 6202 double-sealed bearing is maybe $5 .. very common. If this bearing is toast the brake assembly can wobble around .. whole wheel will probably wobble along with it.
The original freewheel / hub / axel-nut thing is steel. I doubt the original is the problem .. i'm stumped as to how it could have been damaged and it's not the type of thing that you'd turn from brass if it were.. .. maybe something was lost in the translation.
"HERE":http://cgi.ebay.com/ebaymotors/Honda-Hobbit-Rear-Rim-Moped-Parts_W0QQitemZ4567338680QQcategoryZ34284QQssPageNameZWD6VQQrdZ1QQcmdZViewItem is the ebay wheel that got sold.