Every time I drive my Dune Buggy through a town or shop area people ask where I got it from so my friend made a video on how to get one, check it out if you'd like.

www.youtube.com/watch?v=eKa7Utcp1z0

Basically you go to the vehicle vendor in the Headlands Transit Depot, it costs 14500 scrip so you might need to save up for a bit.