Enduring 6FM18 6-FM-18 12V 18Ah Sealed Lead Acid Replacement Battery: BatteryClerk.com Sealed Lead Acid
Dynavolt 6-FM-18 Battery - Replacement Battery for the Dynavolt 6-FM-18 Battery $34.00
Mighty Max Battery 12V 18AH SLA Battery for Enduring 6FM18, 6-FM-18 Rechargeable Sealed Lead Acid 12180 Backup Power Batteries in the Device Replacement Batteries department at Lowes.com