I have been looking on the ebay of Japan for HVX200 related stuff here (you will be able to see the pictures, if not read the Japanese)
http://search.auctions.yahoo.co.jp/search/auc?p=hvx200
but at the moment there are only new cameras and some generic batteries at about 60USD = 35 UKP a throw. There are no p2 cards even though the auctions are awash with every other type of memory.
I would have thought that if they exist they would be on yahoo auctions japan, so I guess that they do not exist yet. And according to a post on this or another forum they may not be all that fast in coming because they contain more than just memory but some sort of processor too.
I guess that a hard disk with firewire is the way to go. Or just carry a laptop around and port to that every few minutes. I can't even afford the Raylight converter software to let me use Sony Vegas yet so I will be using MiniDV and it will be a while before I get any more memory. Someone else paid for the camera.
Tim