Search ebay for "seascooter" and you'll find them for under $200. Even some chinese made versions for about $100 shipped. I've been thinking about getting one, probably would be fun to take along with the boat...
I think Sea Doo makes two different ones. One is like 200, and the other is 370. You can tell the difference by the color of the handle. The more expensive one has a black handle. It can dive to 65'!
