Yeah, the only one I have only seen like 2 for sale.
One was on some euro ebay and went for way too much money.
The other one was on a bike that was sold in europe that went for almost nothing.
Watercooling adds a lot of complications for not a lot of gain. You see it a lot in modern scooters that have had their balls cut off by the EPA. Its a little different when the system was designed from the ground up for watercooling, as opposed to making it work on a moped.
In my opinion there are already so many little problems that pop up on kitted bikes, that adding scalding hot liquid and a delicate system that if it fails would probably result in major damage just isn't a good idea.
I actually made this exact same post last year. I found out they made them, and I was like oh damn I need one. Then I found out that they are impossible to get and not easy to run so I just went with a regular kit and pipe and was very pleased with the results.
The hobbit has a lot of potential. An air cooled system will get you going as fast as you want to go. Trust me.
What you could do if you wanted to run a little leaner would be to set up some kind of forced air, either off of the battery or from a cowl or vent funneling air onto your cylinder.