They aren't very cheap, but the ones worth buying cost around $600 and up.
*THE* place to buy them is gpscity.ca, they have by far the best prices outside <a href=../autolink/redirectpage.php?linkid=78 target=_blank>ebay</a>.
This one has everything you need, and it works well
http://www.gpscity.com/gps/brados/53143.1.9989147131112046800/quest It's very easy to use (click on the movies on that page)
Here's another one based on a PDA. It's not as integrated as the above Quest model, but since it's just a PDA with an antenna and special software, you can use it like a normal PDA too.
http://www.gpscity.com/gps/brados/53143.1.10137888750412046800/ique3200
You can buy a PDA and add a receiver for it, but it's not as nice (it's still a PDA, not really designed with car navigation as a priority).