Dome Light (door jamb) switches - '74 Duster

I am having trouble finding a good set of dome light (door jamb) switches for my '74 Duster.

Mine appear to have a larger than normal thread. I measure the thread to be closer to a 1/2" in diameter. The switches that I can find locally are 3/8-24. They are way too small.

Where can I find the correct kind of dome light switch for my '74 Duster?