Diamond K601 Hideaway trunk mount may be for you.
check out http://www.rfparts.com/diamond/k601.pdf
I have one on my Toyota Camry and a Diamond SG7500 dual bander on it. The antenna is always connected and it takes 10 sec to bring it to or down from operational position including opening the trunk and getting out and back in the car from the driver seat.
It may take some time to find a right position where to mount, so that the antenna does not get on your way when folded inside when you are putting something in your trunk, and the trunk lid does not hit the mount and closes properly. In my case because of Camry's trunk lid shape I had to fold down the rear seat and look from inside the car with the trunk lid closed to find a good spot.
Note that K601 is designed to work with antennas not requiring grounding, though this is possible to modify it a little and run a peace of ground strap (not a heavy one) to the inside of the trunk.