Just now noticing how few options there are for xxs in the US

For reference, I’m 5’3. I’ve been losing weight (on purpose) and have started wearing smaller clothing. My waist is currently 24 inches, and it feels damn near impossible for me to shops for pants and skirts that actually have the waist measurement that fits me. Also, I’m still losing weight, and I’m getting increasingly annoyed by how few options are available on the websites/in the stores I used to like. A bunch of places only have size small, and if they carry XS it’s sometimes with waist measurements up to 25.5.

What’s the deal with this? I feel like I see plenty of women on my college campus that are the same size or smaller than me. Where are they getting all their clothing…?