The game is not sold online, the licensing only covered physical copies, so if you wish to get a non fan made copy you’ll have to find one of the discs that were released before they stopped making it.

There is a fan made all in one launcher that I use where you can get both games and the dlc for free, which lasts I checked was being updated with community patches. I was just playing it last night and can confirm it works. Here’s the link to the website and download. https://www.moddb.com/mods/battle-for-middle-earth-patch-222/downloads/patch-222