I am always missing the right battery for the right device! For these cases, I have 3d printed an adaptor to fit AAA batteries into my GPS (Garmin GPSmap 60cs).
You need as well 2 screws (M5 x 6) for the contacts. I have cut them to the right dimension.
Drawing:
![Drawing of AAA to AA adaptor](/images/adaptor_AAA_to_AA.png#joomlaImage://local-images/adaptor_AAA_to_AA.png?width=736&height=459")
Happy Hiking!