So, I finally found me a yellow one today. I was digging through one of Wal-Mart's *%^*^&%!!! dump bins today. I knew it was the right assortment for the yellow Silverado, but I was about to give up and walk away when I saw a yellow tailgate peeking up at me from deep in the bin. I pulled it out and kept digging, but never found anything else.
Also, earlier this week I stumbled across this HW Road Trippin' Silverado. I don't know how I missed that it even existed. Unfortunately, I only found one of it as well, so I'll be looking so I can crack one open.