I have two spares in good condition you are welcome to have for free if you can remind me the best way to ship them:
I can't find any to purchase locally. The last time I bought any was from Chevy Duty (ClassicParts). I think they are in Kansas, although I don't know if they sell the sockets by themselves, or if you have to buy a whole harness.
Let me know if I can help. Regards, Mark.
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I just noticed the ones I have may not work, they only have two wires each, and yours appear to have 3 wires.