On February 4, 2017, at a relay race event to promote Heads Together at Olympic Park, Kate brought out the matching earrings to her 167 Button pendant necklace.
We were not sure about their provenance at first, but after examining photos I contacted Asprey and received confirmation.
The earrings’ components are the same as the pendant: “central amethyst stone, surrounded by pave diamonds, all set in 18ct white gold.”
Here they are on Kate.
I do not currently know the price for these. If I find one I will update.