Android : Removing a button from a customized Android 2.1 status bar

The Nook Simple Touch has some custom buttons in its status bar. I want to remove the "last book" button. Where is the status bar layout defined? I doubt my apps can modify it through the SDK, but the device is rooted so I can poke around in the system files as needed.

This screenshot shows the status bar, with the button I want to remove on the left:

I've considered hiding the status bar and reimplementing the clock and battery icon in an action bar, but I'd like to avoid that if possible.