I don't have a part # but, in 20 years of owning my 59 Suburban, I never was able to fine a new one. I think I finally bought one for a 60's Chevy, it had an extra terminal on the back for the washers, and requires a bigger hole in the dash but the wiper konb is the same (as long as yours has the hole in it for the washer button). I drilled out the original nut (wanted to used it as a washer) and bought a couple of 1/2-28 jamb nuts off Ebay. That worked great and I kicked myself for waiting so long to do it.
I think this is one like what I bought. https://www.americanclassic.com/1964-66-Wiper-Switch-Two-Speed-W_-Washer/productinfo/67%2D648/
