Portable/waterproof equivalent to the Hitachi Wand

I have a Hitachi wand and it is a fantastic device, but it is somewhat limited by the fact it needs a mains plug to operate. Can anyone recommend an equivalent with the same sort of power as the Hitachi wand, but battery operated, and waterproof. I see a lot of waterproof looking devices on various retail places, and they always say they are powerful devices, but I suspect in most cases that will be marketing fluff more than anything, so I am really looking for actual recommendations from real people, so I don't end up buying a lemon. Any help much appreciated.