Amazon.com: ALAMSCN 3.3V 5V MB102 Solderless Breadboard Power Supply Module with 9V Battery Clip Power Cable 2.1x 5.5mm Male DC Jack Plug for Arduino (Pack of 3) : Electronics
LithiumWerks ANR26650M1-B, 3.3 Volt, 2.5Ah, Lithium Iron Phosphate (LiFePO4) Battery
snapVCC 3.3/5 V regulator snaps onto 9V battery from Electronut Labs on Tindie