I don't know why GM uses junk switches. They really are poorly made. Still, try
http://www.20thstreetauto.com/
or
http://www.contemporarycorvette.com/
or
http://www.tabercorvetteparts.com/index.html
They should have them from cars they are parting out and will guarantee them.
www.whiteracingproducts.com also were fixing clusters so they might do switches, I don't know for sure
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