Since you're new, let me clue you in on something...
This forum is focussed on installing full-on PCs in vehicles. We tend to eschew the all-in-onbe units like you describe in favor of something we build ourselves (for the most part).
As a result, you aren't going to find a lot of information about what you're looking for. A better alternaive is
http://gpspassion.com or a similar forum focussed on
JUST GPS hardware.
You're welcome amongst our ranks either way. Maybe you'll catch this bug.
