Button Cell Battery, Watch Battery, 30mAh, Silver Oxide 1.6V
From Amazon
Varta V370 SR920W 1 1.55V silver-oxide button battery
Conrad Electronic
Varta Button cell SR69, SR921 1.55 V 1 pc(s) 30 mAh Silver oxide 48008
BatteryUpgrade
VartaV370 / SR69 / SR920W Coin cell battery (Amount 1)