Mighty Max Battery ML15-12- 12V 15AH SLA Battery- PACK OF 2 Rechargeable Sealed Lead Acid 12150 Backup Power Batteries (2-Pack) in the Device Replacement Batteries department at Lowes.com
Amazon.com: PowerStar® 12V 15AH Replacement Battery for Peg Perego Gator HPX Toy or Riding Car : Health & Household