Hypernym for "necklace", "bracelet" and "anklet"

There is 'circlet'

noun

3 - a ring-shaped ornament, especially for the head.

www.dictionary.com

Circlet may work for you; it's a bit shaky, but jewelry houses clearly often use it to refer to pieces intended to be worn as necklaces, and some sources at least define anklets and bracelets as types of circlet.

The term bangle could definitely be used to encompass anklets and bracelets, but perhaps not necklaces. I'm not sure there is a word which describes concisely all three

I don’t know much jewelry terminology (and I don’t know anyone whose wrist and ankle circumferences match that of their neck), but this O’La Vi Jewelry ad might be talking about what you’re asking about and it uses “wraparound” as a single word together with “jewelry” (= “wraparound jewelry”) to describe “[jewelry] that contours to [the] shape ... [of] the trait you wish to emphasize.”

Unless the context was absolutely clear, you’d have to use it together with “jewelry” (so I guess that’s two words) because “wraparound” used by itself would refer to a type of clothing, e.g., skirts. (from Merriam-Webster)