Mine was broken when I bought the truck (NP205), I don't really need it but I was doing some other dash stuff and it bothered me that it didn't work, can't find on the internet anywhere, so I bought a generic starter switch from NAPA:
https://www.napaonline.com/en/p/NW_786105, gutted the switch and dremeled out the plastic from the inside enough so that the threaded part of the switch would fit down inside. There is a spring plunger on the end of the little rod, I immobilized that by filling it with JB WELD, then affixed the nut onto the end of the metal part of the switch with more JB Weld, then screwed the starter switch down into it......it worked great except that once it was installed the 4x4 light came on in 2wd and neutral only....so the switch is supposed to be NORMALLY CLOSED. Keep in mind this is not reflected in the Chevrolet wiring diagrams. SO I had to re-engineer the switch to be normally closed. Screwed it into the transfer case and and adjusted it to work properly by using the screw thread on the starter button, then locked it in with even more JB Weld.
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Is it stupid? Yes. Does it look like crap? Yes. Does it work? Yes. If you could find a normally closed button it would be a lot simpler, and if this stops working I'll probably explore that route.