Amazon.com: Replacement for APC Back-UPS ES 350 BE350R Battery - Compatible UB1234 Universal Sealed Lead Acid Battery (12V 3.4Ah 3400mAh F1 Terminal AGM SLA) - Includes TWO F1 to F2 Terminal Adapters :
MIGHTY MAX BATTERY ML3-12 APC Replacement for Back UPS ES 350 Battery MAX3424222 - The Home Depot
Replacing Battery in Back-UPS ES UPS | Schneider Electric Support - YouTube
APC Back-UPS ES 350VA, 120V - BE350G | APC USA
Battery kit for APC Back UPS ES 350 replaces APC RBC29