So, I needed C cells for a bullhorn and I stopped buying normal batteries because they've destroyed hundred of dollars of my electronics.
What to do?
Use adapters like this to make my rechargeable AA size batteries work in a C size hole. This will not work with your little soldier so get your head out of the gutter.
These little numbers work well. The batteries lock inside but is still easily removable, and the adapter is only slightly larger than a normal C cell battery.
Warning: this may not work in all devices as they are not the right size per say and the contact site of C batteries is much larger.