American 3B Scientific has some great gifts for the geeky gal in your life — molecular jewelry!
Earrings are $45 and necklaces are $85 and made from sterling silver!

Caffeine.

Theobromine (Chocolate).
*Also available as earrings.*

Estrogen.

Serotonin.
*Also available as a necklace.*
[Via NBC News]
I'm afraid I don't know any geeky prostitutes at the moment.
I can't find the jewelry on that site.
Anyway, the actual website where they make them is: http://www.madewithmolecules.com
I got my serotonin necklace years ago :)