There is a developer preview of Windows on Arm which you can sign up for. And you can install it on a beta version of Parallels. It works as well as can be expected for pre-release software, and doesn't require you to find keygens and install images on torrent sites or anything like that.
I'm pretty sure Microsoft will make this available for purchase at some point, possibly as something you can buy from Parallels / VMWare as an add-on for their products. There is certainly a market for it, and I'm sure they won't object to making money out of it.