Disposable Battery, Alkaline 1.5V
From Amazon
GP Batteries AA Ultra Plus Alkaline Battery - Chrome/Black/Red (Pack of 4)
Kenable
GP AA 1.5V ULTRA PLUS High Performance Alkaline Battery [4 Pack]
Discount Discs
GP Rechargeable AA NiMH 2500 mAH batteries - GP250AAHC - C4 (4 pack)