You are not going to find those fabrics for sale in any stores. Pottery Barn will have had a staff designer create the patterns, and then commissioned the fabric to be printed just for them.

That's how it almost always goes with ready-made things like that. Companies want their products to be unique.

In some parts of the world (Los Angeles, occasionally but not often NYC), there are "remnant" stores that get their hands on the ends of the bolts from companies like that, but they're sold in the stores only. And they're not every company (bcs the sheets are made across the ocean, usually).