FirstPower FP645 6V 4.5Ah Sealed Lead Acid Replacement Battery: BatteryClerk.com Sealed Lead Acid
Amazon.com: AJC Battery Compatible with FirstPower FP640 6V 4.5Ah Sealed Lead Acid Battery : Health & Household
Mighty Max Battery ML4-6 - 6 Volt 4.5 AH, F1 Terminal, Rechargeable SLA AGM Battery - MightyMaxBattery
MIGHTY MAX BATTERY 6V 4.5AH SLA Battery Replacement for FirstPower FP640, FP645, FP660 MAX3864470 - The Home Depot
Mighty Max Battery Replacement for FirstPower FP640, FP645, FP660 Rechargeable Sealed Lead Acid 645 Backup Power Batteries in the Device Replacement Batteries department at Lowes.com