You probably have some really cool, free aaaa batteries sitting around at your home, and may not even know it! What you need: 9 volt battery, Needle nose pliers, Wire clippers (maybe)
Step 1: Remove the Metal Battery Casing
However you want to do this. Using, pliers and/or wire clippers.
Step 2: Keep Disassembling
Remove any other plastic/metal casing around the aaaa batteries.
Step 3: Remove Joiners
There's these little metal strips holding the batteries together. Those come off, too!
Step 4: Done!!
You'll end up with about 6.
Step 5: But What Are These Good For?
aaaa batteries are interchangeable with most aaa battery roles. They're also smaller, and lighter. (Note, not all 9 volt batteries contain these. I know for sure Energizer and Duracell do).