I got it from here: http://alpha.gnu.org/gnu/emacs/pretest/windows/

It works flawlessly. I just dropped it (26.1) in on top of my existing setup and had to do nothing else and I'm working away on it right now.

When I was downloading at least, I had to download it and the dependencies separately. The README says there should be a unified zip-file but it wasn't there at the time.

Had some issues with Windows 10 refusing to merge the directories from the deps package so had to drop to a cygwin shell but it actually worked quite well even without the deps.

Flyspell in Emacs 26.1 seems to require a version of Aspell that is not officially available for Windows. I might need to put off the upgrade until I can attempt to compile a newer Aspell for Windows myself.

"Error enabling Flyspell mode: (aspell release 0.60 or greater is required)"

In case anyone else was facing this problem (and isn't too committed to Aspell as a backend for Flyspell), the version of Hunspell from ezwinports[1] (version 1.3.2 at time of posting) seems to be working with Emacs 26.1 on Windows.

[1] https://sourceforge.net/projects/ezwinports/files/

I'm not sure how you feel about cygwin? aspell 0.6 is available from there, and I've just tried it out with emacs and it works well.

An inofficial build is available here: https://www.reddit.com/r/emacs/comments/8n2wga/emax642018052...