KermMartian developed this useful 3d printable AAA battery module that replaces the standard battery and enables you to connect your device to external power supply via wire connection. He used it on his calculator.
Detailed guide and STL files can be found at:
https://www.cemetech.net/news.php?id=760
Detailed guide and STL files can be found at:
https://www.cemetech.net/news.php?id=760