The battery is a standard CR 2032 watch battery (Lithium 3v) that is easy to find at your local supermarket, pharmacy, hardware store or gas station. It sells for about $3.00 USD.
Only use the CR 2032. There are other, similar shaped coin batteries (such as the CR 2025) but they are not the correct thickness for proper power connection to the Pod.
Note! After installing a new battery, we recommend that you sync your Pod to the MilestonePod App before your next run.