Update: Due to localised panic buying because of the coronavirus pandemic, many local stores have sold out of AA batteries. AAs are more popular than the smaller AAAs. If you can get AAA batteries, these can be used to power most AA battery devices in a pinch.
If you run out of AA batteries but have some AAA batteries lying around, you can convert the AAA battery into a AA battery with some tin foil. It got my remote (above) working a treat!
All you need to do is fold up a small piece of tin foil to fit (make up the size difference) at the negative (flat end of the battery with the –) end of the battery. You want enough tin foil to create a firm fit on the battery to ensure both the positive and negative terminals on the device are touching on the positive/negative ends of the battery.
This tip works great at a pinch, but it shouldn’t be considered a permanent solution as the AAA batteries will run down much faster than the larger AA batteries.