Radio Shack is closing out a couple of models of gooseneck cellphone mounts for $10 each.  Possilby because their suction-cup bases scared away customers (it sure gives me the willies to think about an expensive cellphone or PDA being mounted with one).
But...
If you use a nail or screw to tap out the pin holding the suction cup release lever,  you find a hold that you can put about a #10 or so screw through to attach the base firmly.  The previous owner of my truck had attached one of those slide-out mounts for a CB to the roof.  I finally found a use for it:  I screwed the mount to it,  and it holds the Z in a position where it\'s out of the sun,  out of my normal line of sight,  and easy to see when I want to.
To attach the Z to the cellphone holder,  I took the holder apart and removed the \"gripper\" mechanism (which doesn\'t spread quite wide enough to hold the Z.  Dammit),  and tie-wrapped the \"Strongarm\" bracket out of a Case Logic case to it.  I drove around for a while to make sure the idea was going to work,  and it did.  So I\'ll drill a couple of holes and screw the bracket to it.
I don\'t know how the stiffness of the gooseneck compares to the new models,  because I\'m too cheap to spring the $25 RS wants for them.  But it\'s a lot better than the microphone gooseneck RS sells,  which flexes too easily for vehicle use.  I put a 90-degree bend in it to hold the Z vertical with the base mounted parallel to the roof,  and it doesn\'t seem to flex visibly at all.  Even in my \"camper special\" pickup,  which rides like a buckboard if it doesn\'t have a ton or so of load on the bed.
So,  for about $25 ($10 for the mount,  and $15 for the case at places like Fry\'s and Circuit City) and very little work,  you can make a really solid mount that fits the Z very well,  and is probably even solid enough for off-roading.
fwiw:  I dunno whether it was just the particular units I got,  but the model for fliphones (with a clear phone holder) was easier to remove from the gooseneck part for tinkering.  I was afraid I going to break the plastic when I whacked the larger one to disconnect it.  That may be \"better\" or \"worse\",  depending on whether your goal is to have a system that\'s \"extra safe\" or \"easy to mess with\"  ;-)