Uh, Clarion is hardly a non mainstream vendor

They make some of the nicest car audio systems out there.
The Garmin Streetpilot 2730 and 7500 have XM radio built in, but you are looking at >$1000...
If you are looking for a handheld unit, then the Busnell
Onix 400 would fit the bill.
But can you help us out with your exact requirements? And why you want them combined? By portable, do you mean something you can take on a hike with, or something for in the car that can be taken along with you?