I found a similiar chrome cap / plug in lowes hardware; I believe they are for facuet caps. I place one on each side of my (65 model in gallery) door channels under the upper door hinge. I also have seen emergency flasher on 67-72 F600 truck OEM in the dash bezel's. I got a buddy with one on ebay going for sell right now.

Mitch

 

I bet the Hazzard swith was located in the glove box for the passenger to switch on when they saw the driver jump out to start pushing the truck off the road....No? Mabey they thought there were too many wires in the column to begin with. By the way, check with the resto parts mag for OEM stuff. I like their exploded parts pics. Its easy to find what your looking for.
--------Kevin