If you run out of a charge on a pair of AA batteries but have some AAAs laying around, one suggestion is using a strip of tin foil to convert the AAA battery into a AA battery.
To get this to work, all you need is a AAA battery and some tin foil. Wrap up a ball of foil and stuff it into the case of your device where the battery’s negative terminal connects. As long as you have enough foil to fill in the gap, your device should turn on. This method works great if your mouse battery dies in the middle of a work day or if a flashlight goes out during a storm. It’s not a permanent solution and should only be used in a pinch, but it works great for short periods of time.