Philips Advance Optanium 120/277-Volt 4-Lamp T8 Instant Start Electronic Fluorescent Replacement Ballast 520387 - The Home Depot
GE UltraMax Proline Electronic Ballast, 120/277 Volt Instant Start Ballast, Normal Ballast Factor, Ballast for Fluorescent Light (1) or (2) Lamp T8, Compatible with F32T8/WM and F17T8 - Electric Plugs - Amazon.com