The game is no longer sold online. It is legally abandoned by Epic, Steam, GOG, etc., and is free to download... You can download Unreal 2: The Awakening from legitimate digital storefronts like
GOG.com or
CDKeys.com, or find the original game files on the Internet Archive. The game is also now freeware, and the files may be available through OldUnreal.
To use Resade with Unreal II, you will need to manually install the DX8 to DX9 file:
https://github.com/crosire/d3d8to9/releases (for example, version 1.13.0 is available as d3d8.dll). Download the file and place it in the game's directory (e.g., G:\Program Files (x86)\Unreal II Special Edition\U2SP\SYSTEM).