Amazon.com: Synergy Digital Smartwatch Battery, Works with Garmin Fenix 3 HR Smartwatch, (Li-Pol, 3.7V, 300mAh) Ultra High Capacity, Compatible with Garmin 361-00034-02 Battery : Electronics
Original Replacement Battery For Garmin Fenix 3 Fenix3 F3 Hr Gps Sports Watch Battery 361-00034-02 Watch Genuine Battery 290mah - Mobile Phone Batteries - AliExpress