Amazon offers its Prime members the TP-LINK 300Mbps 802.11n Wireless Mini USB Adapter, model no. TL-WN823N, for $14.99. Clip the $7 off coupon to cut the price to $7.99. With free shipping, that's the lowest total price we could find by $7. (Non-members can spend $35 to qualify for free shipping; otherwise, shipping adds $8.09.) It features 1-touch encryption via the WPS button.