Okay Eric, you can download the app from here...
click
Once you've downloaded it, double click the file to run it. When it's running a green icon with a white 'H' will appear in your system tray.
Alt + b will toggle the game screen size between 1920x1080 and 1024x768
Alt + x will close the app.
If you want to change the shortcut key, you'll have to let me know so I can edit the app and re-upload it. The same goes for the game window sizes. You are not limited to the in-game resolutions, you can have whatever size you want.
Scott.