Ultralife U9VLJPFP, 9 Volt, 1.2 Ah, "9 Volt" Lithium Battery
Amazon.com: Replacement Battery for Compex Mi, Mi-Sport, Enegry,MI-Fitness,Runner, Theta 500,Physio 5,FIT,SP 2.0,fits Part No Compex 941210 4H-AA1500, 4.8V Ni-MH 2000mAh/9.6Wh : Health & Household
Amazon.com: Replacement Battery for Compex 4H-AA1500 941210, Compex Mi Mi-Sport MI-Fitness Runner Enegry Mi-Ready Vitality PerformanceE Mi-Ready FIT Sport Elite Enegry Edge US Performance US : Cell Phones & Accessories