Casio FX-8700GB Battery Conversion

This old calculator uses 3 CR2032(plus another one for the backup) and depletes the battery in just a few days. Build this battery case to convert it to use regular 9V battery and a switch to turn the power off completely, so that it probably can last for a very long time. The case might also fits other models in the same era, like FX-8700G, but I'm not sure about others. If the layout looks the same, it probably fits.

Materials
2 used CR2032
Thin wire (I use 30ga)

Optional:
Rocker Switch 12mm x 8mm (prefer to have it, just in case need to power cycle)
9V Battery Connector (I just soldered the wires directly to the battery)