Put a 9v slot on the back for easy access. That would be sweet
Discussion
That's what I was thinking. Be really easy for anyone to use their own 9v and cheap. I'll make the 3D file available for free once I finish it.
9v is bad juju -- not enough ooomph to reliably power the battery. When someone says their camera isn't working, my first question is whether they're trying to power the signer with a 9v battery.