I fitted one of these:
link
�19 delivered, fully waterproof, and seems well made. The only problem I had was finding somewhere on the handlebar to mount it - there wasn't anywhere. I ended up fixing it to the right hand crash bar, just in front of my right knee. It's quite unobtrusive there, but whether it will be convenient for the satnav (the main purpose of fitting it) remains to be seen. I may well re-mount it somewhere else if it proves awkward.
I quite like flush-fitting sockets, but there's not a lot of panel area on the XTR for this.
(Update, having now read the post above): When I had the Bonnie (which I fitted with a Triumph accessory socket of the DIN variety) I promised myself that I would go over to DIN exclusively. It never happened. It meant that every device I owned would have to have a dedicated DIN cable, and I ended up with a splitter cable with cigarette sockets on the end just for convenience. The DIN system is mechanically superior, no doubt about it, but in the real world I have never had a problem with a good-quality, weather-sealed cig-type socket.