Costco is starting to get more gluten free foods
Last time at the Seattle Costco they had large signs near gluten free displays which was nice. They also had more products that are gluten free. The Tortillaland uncooked corn tortillas, Glutino products and some others. They also have a gluten free Sriracha from Sky Valley that is very good. My wife is GF [I'm only sort of GF] but this will be very helpful.
I go to the Costco on 4th South in Seattle and they regularly carry two kinds of almond flour, as well as Mary's Gone Crackers cookies and Crunchmaster crackers...all in huge Costco sizes.
Costco is a business and right now gf=$$. So of course they are expanding their assortment.
Also look for crunchmaster crackers, hemp seeds, quinoa, wild rice blends, and naturally gf foods that are minimally processed like polenta and edamame.