Custom Alkaline Battery Pack: 3 x 9V and 1 x 13.5V (27xAA) with Molex Connector
9V High Capacity Rechargeable Battery Pack - BX948
Amazon.com: ENEGON 9V Direct USB Rechargeable Lithium-ion 650mAh Batteries with 2 in 1 Micro USB Cable for Micro Phone, Smoke Alarms, Electronic Toys, Walkie-Talkie and More Devices (2-Pack) : Health & Household