Watson Lithium-Ion Battery Pack (3.7V, 1800mAh) for HD B-1801
Lithium Ion battery - 3.7V 4400 mAh
Amazon.com: DC 3.7V 3000mAh 103665 Rechargeable Lithium Polymer Replacement Battery for DIY 3.7-5V Electronic Product, Mobile Energy Storage Power Supply : Electronics