A good quality 22650 button top battery. The flat top version of the battery can be foundhere.
PKCELL ICR17280 Li-Ion Button Top Rechargeable Battery - 3.7V 600mAh
18500 3.7V 1500mAh Button top rechargeable battery for flash light, garden light
18500 3.7V 2000mAh BUTTON TOP rechargeable battery Diameter 18mm x Length 50mm
2pcs 26650 Batteries 3.7V Rechargeable Battery Button Top
18650 Battery Charger with 4 Pack Ni-MH 3.7V 3500mAh Flat Top Rechargeable Battery, 4 Bay LCD Display Smart Universal USB Dual Battery Chargers for 18650 18500 21700 26650 14500 16340 Batteries, Boxed
2-8X 26650 Batteries 3.7V Rechargeable Battery Flat Top, 4Slot USB Charger
