Nano size( 16mm×32mm×3.0mm, 2-3 grams weight ): This sits discreetly inside a USB port. This has internal antennas which perform well in most scenarios. Just plug in and connect to WiFi. If you're running an older version of Windows, run Windows Update to get the drivers installed or search "RTL8811CU " on google and download drivers from Realtek's website.
eBay