Does anyone know where I can buy a key for Windows XP 64-bit??

I’m trying to install Windows XP 64-bit to prove a point and can’t seem to get a key anywhere online that isn’t free and I need a unused key to activate a legitimate version of Windows XP
Nowadays, it is not really possible to find Legitimate Windows XP keys. You can search on ebay, but most likely, they are not going to be legitimate.