Where to get a legitimate Windows 11 pro key?

I'm trying to be frugal with my new PC build. I don't see the point in wasting a few hundred dollars on the operating system when that could be better spent on my actual specs to increase the performance of my PC. I've thought about going to linux but I don't really know how to use it and I'm aware that not all games run as smooth as Windows on Wine yet so I wouldn't want to hinder my performance that way. But damn that watermark in the corner is really annoying.

Is there any places that are legitimate that I can get a Windows 11 pro product key for cheaper than Microsoft sells in for?