TP-Link N150 TL-WN725N. 1. An ultra-cheap, super compact WiFi adapter that only supports 2.4GHz 802.11n connections up to 150Mbps. See it at Amazon. Product Specifications. Wi-Fi Technology.

The community has identified at least one RTL chipset that works and it happens to be in the TP-Link TL-WN725N. These are old 2.4 GHz only units, so they are widely available for $10 or less.