LSS271621 Battery for Fitbit Charge 3 FB409, 70mAh - sold by smavco - Walmart.com
Fitbit Zip Battery Change - YouTube
Amazon.com: Fitbit Versa 3 Health & Fitness Smartwatch with GPS, 24/7 Heart Rate, Alexa Built-in, 6+ Days Battery, Black/Black, One Size (S & L Bands Included) : Sports & Outdoors