Battery Holder for E-420 (and E-500): Olympus SLR Talk Forum: Digital Photography Review
Amazon.com : Replacement for Olympus E-420 Battery and Charger - Compatible with Olympus BLS-1 Digital Camera Batteries and Chargers (1150mAh 7.4V Lithium-Ion) : Electronics
Amazon.com : Replacement Battery for Olympus E-450, EVOLT E-410, E-620, E-400, E-420 (BLS-1, PS-BLS1) : Digital Camera Batteries : Electronics
Olympus E-620 Review
Olympus PS-BLS1 Spare Battery for Olympus Evolt E-410 and E-420 - Van Tuil
Amazon.com : Replacement Battery for Olympus E-450, EVOLT E-410, E-620, E-400, E-420 (BLS-1, PS-BLS1) : Digital Camera Batteries : Electronics
2x 900mAh Olympus Kamera Ersatz Akku BLS-1
Olympus E-420 Battery and Charger with Car Plug and EU Adapter - Replacement for Olympus BLS-1 Digital Camera Batteries and Chargers (1150mAh, 7.4V, Lithium-Ion) - Walmart.com
Olympus E-420 Review: Digital Photography Review
Amazon.com : 7.20V,900mAh,Li-ion,Replacement Digital Camera Battery for Olympus E-400, E-420, E-450, E-600, E-620, E-P1, E-P2, E-PL1, EVOLT E-410,Compatible Part Numbers:BLS-1, PS-BLS1,BLS-1, : Electronics