Where are 'alphas' stored under SP 2022?

I've recently updated to Substance 2022 (Designer and Painter). I've found that several of my Designer projects don't open, because it can't find some "alphas" I was using, that were part of the Substance Painter shelf. One example is: "square_rectangle.sbsar". I've tried searching for this, and although I still see this alpha within Substance Painter, I can't find the SBSAR file on disk to point Substance Designer at.

Could someone tell me where these files ended up? These aren't my own custom alpha. They're built-in to Substance Painter, but I've having trouble finding them on disk.

Thanks.