Small sized GPG command-line tool for Windows
Solution 1:
You could download it and compile it yourself here: http://www.gnupg.org/download/index.en.html
The command line version is included in the GPG4Win, but the installer is actually quite helpful, and I would recommend that myself. (current gpg2.exe that is included is 769kb)
Also see the light version here: http://files.gpg4win.org/gpg4win-light-1.0.9.exe