Welp, time for some brave and naive soul to fork up $400 and put the debate to rest
Interesting. Seems to be a whole section devoted to the GM Accessories I'd always heard about but never seen. As in, I've seen talk of official accessories but have never EVER seen one. Like the ski carrier. Or the "highway emergency kit" #12497328. Or an official emergency reflective triangle! #22745654. This website is a hoot.
And I found a part number for the assist steps I have! Apparently they WERE an option on the TrailBlazer. I've never ever ever seen another TB with them. Search "GM 12498709" on Google Images, first two results are the style I'm talking about.
Also under the chevroletpartspeople.com website they have organizer trays that fit the cargo area. GM Accessories, why must you be so hard to find when you have such neat stuff!?