Yeah, I’ve gone the third-party route myself got a Windows 11 Pro key from Noxkeys.com for about $13, and it activated just fine. as long as you get from a site with good reviews and support, it’s usually safe. Most of these are Retail keys, so they’re cheap but might be tied to one machine.
Just make sure you download Windows directly from Microsoft to avoid any shady installs. It’s not always clear-cut legally, but for personal use, most people never run into any issues.