I was recently trying to track down a TP-Link TL-WN821N USB WiFi adapter to use for my WDTV Live.
As you probably know the official support page only lists V2.2 as a supported version.
TP-Link are up to 3.x now with their latest models.
I was trying to source one 2nd hand, so I emailed TP-Link to confirm which models share the same chipset as 2.2.
Here was their response:
Thank you very much for your email requesting information about our product.
The hardware V1 and V2 have the same chipset: AR9170+AR9102.
By the way, the hardware of V2.1 and V2.2 are both V2, so the chipsets are the same.
Hardware V3 has a different chipset: AR7010+AR9287.
Given this, I would expect that any V1.x or V2.x model of the TL-WN821N should be compatible with the WDTV Live.
Hope this helps.