UpStart Battery Epson LB-01 Battery - Replacement for Epson CR-V3 Digital Camera Battery (1300mAh, 3.3V, Lithium-Ion) - Walmart.com
esp8266 - 3.7v to 3.3v voltage regulator - Electrical Engineering Stack Exchange
Lithium Werks ANR26650M1-B, 3.3 Volt, 2.5Ah NanoPhosphate® Lithium Ion Cell
It Just Got Easier to Convert Lithium-Ion Battery Voltage to 3.3V with this Efficient Single Inductor Synchronous Buck-Boost Regulator | Analog Devices