Sabrent High-Power NT-WGHU Long-Range WiFi Wireless USB Adapter for $12.99 shipped.  Here is a screenshot for your reference.  It complies with wireless IEEE802.11b/g and has 1000mW transmitter output power, antenna connector RP-SMA female, detachable 6 dBi dipole antenna, 5-foot USB extension cable, and more.  Most places have this high-power USB long-range Wi-Fi adapter for about $19.