That link doesn't work for me. Has an extra "htpp://" in it.
this should.
http://www.cars-on-line.com/parts1334.html
According to the ad those are black rivets. Don't think GM ever used black ones. Dodge did.
There was a guy selling both the natural and the black ones on ebay, but apparently he ran out, as I don't see any for sale now.
These may be correct for GM.
http://www.cars-on-line.com/parts750.html
phone number is NH, so may be the same seller as the black ones.
$45 to $50 per pair is not out of line. Getting pretty hard to find.