there is one on ebay right now:
http://cgi.ebay.com/Authentic-Marc-Jacobs-Blake-Handbag_W0QQitemZ170184055429QQihZ007QQcategoryZ63852QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
it would be a good idea to get the bag authenticated first, but it looks okay to me so far.