DOS - Where can I find tee for Windows?

There is no inbuilt DOS command for tee, either internal or external.

A few options:

You can download tee by Zuga.net.

For bug reports and enhancement requests, please use the about form.

C:\Users\Zuga>tee /?
tee by Zuga.net
Usage: tee [FILE]

You can install Cygwin:

Cygwin is a collection of Linux utilities compiled for Windows.

C:\Users\Zuga>tee --help
Usage: tee [OPTION]... [FILE]...
Copy standard input to each FILE, and also to standard output.

You can use Windows Powershell:

PS C:\Users\Zuga> get-service | tee services.txt

tee is an alias for Tee-Object.

PS C:\Users\Zuga> get-alias tee

CommandType     Name                    Version    Source
-----------     ----                    -------    ------
Alias           tee -> Tee-Object