Lone Star State
I thought I had a good replacement, the screw I bought looked identical, but I couldn't even get it to screw in, the threads wrong pitch, etc. I bought a #8 Phillips Truss Head. I'll give the metric a try, that's what I should have done previously.
Amazon: Amazon.com: Clipsandfasteners Inc 25 Pillar Trim Moulding Clips Compatible with GM 92139070: AutomotiveI bought ten of the plastic clips at my local Chevrolet dealer. Walked in with that part number above and he ordered ten. Had to come from a warehouse in Michigan. Seem to be readily available. $5 a piece at the dealer.
Looks like this clip has a couple of reviews from G8 owners that said it fits good. I'm going to give it a try.