Oldhat,
I always thought that the sync charge cables between most Zaurii were interchangeable. In fact on the trisoft and rwsherwood websites they only sell one cable for the various versions.
I bought a cable from Electro Island which charges, but doesn't sync. And I've got an older cable from Expansys I used with my 5500 that used to charge and sync but after a few months now only charges.
I think the real issue here is that a lot of people have had usb sync/charge cables which were defective, and needed to be replaced shortly after purchase. Make sure you buy from a repuatable vendor who will swap out the cable if you have any problems.
My suggestion for the US is to try rwsherwood.com, as he has had positive feedback on this site.