Urbestfriend ran into the same debocle. I bought a Garman Nuvi for Vacation,
then wanted to verify speeds on the five bikes. That Givi bag, although neat,
I believe was around $70.00. For my Xciting 250, I modified the stock bracket
that came with the unit and screwed / JB Welded the mount / arm to the "i.e. Horn"
button on the handle bars. The mount stays, the GPS is removable and very secure.
For my Grandvista, I searched and found "GPSNow.com". They had Garmin Swivel
Base $9.99 just like what came on the sandbag unit, I bought with the GPS as a deal.
The Grandvista (i.e. Horn" button has a recessed center logo. Buy some of that clear
epoxy mold stuff at a hobby store, Micheals, Hobby Lobby, etc. Fill the depression to
the top and then mount the GPS base the next day using the 2-way tape that comes
with the mount. Be selective and you can save some money and still have a successful
installation.