Do you want a bluetooth unit or a hardwired unit?
I have a basic serial GPS hardwired to the car computer as well as a bluetooth Holux GPSslim236 that I can use with my iPaq PDA over bluetooth as well as with any bluetooth computer. Any bluetooth unit you should be able to use with both, but for a permanent solution in the car once you get there I'd recommend a hardwired serial unit (less issues when coming in and out of hibernate/standby).
If you get a normal serial unit you should be able to find an adapter cable that lets you use normal serial devices with your Axim PDA, just do a google search. Not familiar with that specific unit but most pda's I've seen have their little connector at the bottom and it's just a matter of finding that right adapter cable for it.
If you want a GPS that'll work with both I'd stay away from USB units. Though they are simple to use with a normal computer by just plugging into a usb port, I doubt you'd be able to get it work with your Axim, plus I have a lot fewer problems with good old serial devices.