I bought some from a place here local called "The Clip House" when I mounted a console in my old '79 Bronco several years back. They even sold the tool to hold them while you collapsed them into the panel.
Call around your area to places that install truck equipment and do restorations. If all else fails, do a Google search for The Clip House in Colorado Springs and ask if they have any nutserts in stock. Make sure you have the thread pitch you want to use handy to tell them along with the diameter of the mounting hole you are going to use so you get the right size.
Later,
Joe