What’s a cheap GPS tracking unit for a car?

Well, you can get the Garmin eTrex Legend (the blue one). It has a base map of the USA and/or Canada. You can get them used on eBay for as low as $80 US or buy it new for about $139 US. The dash mount is extra though. Good value for the money if you are looking for something real cheap.

Note, it will just show you where you on the map, not the best turns or route to take.