If anyone still wants to get it, may I recommend Gog.com? It's €6,30 cheaper than Steam (or equivalent in your local currency), you get a DRM-free download, not bound to your Steam account. Meaning you an run it anywhere, even without an Internet connection or on multiple PC's at the same time. And it's not like an old games such as UT2k4 have any Steam integration anyway.
https://www.gog.com/game/unreal_tournament_2004_ece