What about a detachable pocket that's a fashion accessory, and you hang it from a strap over your shoulder?

It used to be this way. When women were only "allowed" to wear dresses, often they carried a pocket pouch on the inside of the skirt. It went on like a belt under the skirt.

I wear a phone holder on my belt. There are arm bands, fanny packs, flat stretchy belt-adjacent things. Products exist. We just haven't achieved critical mass of women not interested in carrying purses who are interested in spending the extra shopping effort to find pants or cardigans or button up shirts with near-waist-level pockets (I am discounting boob pockets here).