You will find folders online called DirectX_Redist_Portable . Ignore them. These are just the official Microsoft redistributable packages unzipped into a folder.

Running games from the 2000s-2010s on Windows 10/11.

You have three legitimate options to achieve that "portable" dream:

DirectX Portable is a self-contained, executable version of DirectX that can be run from a USB drive, CD, or DVD, without the need for administrative privileges or a traditional installation. This means that you can carry your DirectX-enabled applications with you, and run them on any Windows-based computer, without modifying the host system's configuration.

DirectX is a fundamental set of components in Windows that allows software—primarily games and video applications—to work directly with your video and audio hardware. Traditionally, DirectX is deeply integrated into the Windows operating system, making it non-portable.