Akodi via Amazon offers the Anewkodi AC600 Dual-Band 802.11ac Wireless USB Adapter for $19.99. Coupon code "AC600WIF" cuts it to $10.89. Plus, Prime members bag free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $8.02.) That's tied with our January mention and $1 under the lowest total price we could find elsewhere. It features a long-range 2dBi antenna and up to 600Mb/s WiFi speeds on 5GHz and 2.4GHz bands.