HTC America has a site with downloads for T-Mobile's MDA, as well as the SDA, Cingular's 2125 and 8125, and the UTStarcom 6700.
I'm particularly interested in Bluetooth GPS units for my T-Mobile MDA Vario. I was browsing through the XDA Developers Forums today and found a reference to the Holux GPSlim 236. A little searching and I found this review at PocketPC Thoughts (which is a good site in itself). Of course, I have to do more research but this looks like a honey!
Wikipedia is a constant source of amazement to me. If this article is to be believed, you're better off to plug your laptop into a power source whenever you have the chance and, above all, do not run it through a deep discharge cycle!