I have ordered RAM's new Aqua mid-sized box to mount on to my K1200RS utilising the 9mm "B" mount off the clutch housing pinch bolt.
The aqua box has a soft-touch front membrane which allows you to use the GPS while it is in the box - I tend not to change destination while on the move, so didn't see that spending £350 or more on a Zumo was worth it - this way I can use the nuvi on my bike and in the car, and for commuting I can put my mobile in there and use my handsfree Cardo Scala headset.
The aqua box has replacement front membranes, should you be ham fisted
Total cost for the mounting kit would be £65 (but I had some spare RAM parts). In the US it would have worked out to under $100, plus shipping.
Parts I used were:
For GPS I went with a nuvi 200W (mostly because it has euro postcode search) - it isn't ideal, in that I can't add routes, just one waypoint, but for Euro-touring it will do the job - but it was cheap and I got full Euro maps for free as an upgrade from Garmin!
The nuvi uses a mini-USB connection, so I have a ISO/DIN 4165 to cigar-lighter and am using a cigar lighter/USB adapter installed under the seat, with a long USB cable into the back of the aqua box. My thinking is if there is a problem, USB cables are cheap!
I have ordered a marine/waterproof cigar lighter socket which I will (eventually) wire into the fairing mount standoff and on a fused link direct to the battery.
I will take pics and post them when it is finally cabled up.
Off on a 3000Mi trip in August, so I will be able to give a better review of how it pans out.