TheGoodBlokes via eBay offers the Microsoft Surface Type / Touch Cover Bluetooth Adapter
, model no. Q6W-00001, for $26.99
with free shipping
. That's $3 under last month's mention and the lowest total price we've seen. (It's a current low by $13.) It's compatible with the Surface RT, Surface 2, Surface Pro, Surface Pro 2, Surface 3, and Surface Pro 3.