熱電冷却モジュールTEC1-12706

These little peltier pads work really well if you want to heat or cool something, and their compact size allows them to fit inside a variety of small objects.

If you want to use this to cool something, make sure to properly suck the heat from the hot side with a beefy heatsink/fan. The one used for CPU works great. Otherwise, it won't work.