I Also had a problem with where to fix a TomTom sat nav, as I have the sony cd, the cd tray type won't fit !.
I purchased a tomtom fixing kit from halfords, it covers all tomtoms, and fixes superbly in the Airvent. of my Focus
It costs £20 But when I told the assistent that it was only worth about £10 to me, He said o.k and sold it me for a tenner ! !