CR 1632 GP: Lithium battery, 3 V, 140 mAh, 16,0x3,2 mm at reichelt elektronik
Amazon.com: Duracell 1632 3V Lithium Battery, 1 Count Pack, Lithium Coin Battery for Medical and Fitness Devices, Watches, and more, CR Lithium 3 Volt Cell : Health & Household