If you get a 2-cell lithium polymer (LiPo) battery, it will last for a very long time and just wire it to the battery terminals inside or make a jack to plug into the camera's power plug.
You can get them in all kinds of capacity. The larger ones should run the camera for months.
https://www.amazon.com/s?k=2s+lipo
The battery is 7.4 volt but will not hurt the camera, as the camera pulls what it needs... the battery does not push. But if you are worried, you can get a buck converter to step the voltage down to 6volt but it is not necessary.
https://www.amazon.com/LM2596-Conver...48&sr=8-3&th=1
Do not let the LiPo battery get below 3.3v per cell - they do not like to be overly discharged.