Glam Hobby via Amazon offers the Ourlink 600Mbps 802.11ac Dual Band Wireless USB WiFi Adapter for $19.99. Coupon code "RDRYH33X" drops it to $8.99. Plus, Amazon Prime members bag free shipping. That's $3 under the lowest price we could find for a similar adapter elsewhere. It features 2.4GHz and 5GHz bands, a detachable 5dBi antenna, and compatibility with Windows and Mac OS.