Source for captured nut to mount arm rest?

[rod1701]

Thanks guys. Maybe I was tired or just needed a little time and distance to rethink it. There are a couple of different plastic license plate nuts, one is a thicker plastic, and the other thinner. I bought what was on the HELP rack at the local PepBoys, which was thicker type. Couple of taps from the hammer and they popped in. Still with the springy part was too snug to pop back out for the screw to fit. Easy fix was to take a drill bit to open up the hole a little. Works perfectly now.