I've found this one which is a bit cheaper.
http://cgi.ebay.com/Macintosh-Authentic-Powerbook-AC-Adapter-M5652-7-5V-3A_W0QQitemZ380006489557QQihZ025QQcategoryZ80064QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
http://cgi.ebay.com/Macintosh-Authentic-Powerbook-AC-Adapter-M5652-7-5V-3A_W0QQitemZ380006489557QQihZ025QQcategoryZ80064QQssPageNameZWDVWQQrdZ1QQcmdZViewItem