Use MeritLine coupon code MLCQ31UN
MeritLine has this Geetek Janus II 802.11n Wireless USB 2.0 Adapter for $29.99. Use the coupon code and the price drops to $19.99. The adapter features dual high-gain dipole antennas, up to 300Mbps transfer speeds, WEP, WPA, and WPA2 support. Shipping is free. Coupon expires after 200 uses.