Not strictly true, the VEXnet key is based around the RT2571WF chipset (often called the RT73), this was popular a few years ago and found in many $10 adapters, however, it’s become almost impossible to find in any currently shipping product. I though I had found an alternative a few weeks ago in a part from TP-Link, the TL-WN321G, but the latest Version 4 keys have switched to another more recent device. Tenda also used these parts but, again, unless you can find them on ebay everything they had has been superseded. Hopefully VEX did a lifetime buy of the RT73 adapter.
To use an adapter based on a different chipset would means new firmware in the joystick and cortex, essentially a different driver, not a simple task.