D LI7 DLI7 Battery for PENTAX Optio MX MX4 750Z 450 550 555 Camera|Digital Batteries| - AliExpress
Pentax Optio 550 Replacement Battery Charger
Amazon.com: Synergy Digital Camera Battery, Works with Pentax Optio 550 Digital Camera, (li-ion, 3.7V, 1800 mAh) Ultra Hi-Capacity, Compatible with Fuji NP-120 Battery : Electronics
Pentax Rechargeable Lithium-ion Battery D-L17 39117 for Optio 550 / 555 / 450 / MX Digital Cameras 39117 — CampSaver