Hm... how bout a drop down oxygen mask like in an airplane?
Maybe you could put a coin holder in there held on via velcro. Or put some kind of a sunglasses holder up there via velcro? None of this is essential of course, plus my 98 has the universal transmitter anyway so just throwing stuff out there
I've seen a flexible "stalk" for GPS units that can mount to glass, plastic, etc. Maybe you could fasten it to the roof inside of the garage door opener bay somehow?