16-Pack AA to C Battery Adapter Converters with Spacer Case - Durable Size Converter for Flashlights, Toys & Electronics - Perfect for Emergency Kits & Outdoor Gear

I have tried soooo many of these adapters on Amazon and these are the only ones I can find that just work easily and well. You slide in the AA battery and it clicks into place when the button-top side of the AA cell protrudes the right amount, which is more than enough clearance for the button to be well exposed as well as the shoulder of the AA cell.That's important because other adapters open up (and fall apart) and must clip together and are usually too big and the button top doesn't stick out enough for many applications. No such problem with these. Also there is enough of a radius on the C cell (adapter) corners that they don't fight going in next to each other.Best ones I can find on Amazon - I won't buy any others because they're a hassle. These just work, and work well.