660093-001 - HP 660093-001 battery flashed back write cache (fbwc) capacitor pack 54v with 36 inch cable for smart array controller p222 p420 - serverevolution.com
660091-001 Battery 5.4V HP Flashed Back Write Cache Capacitor P420 P421 B320i P822 | www.batteryclub.org
HP 660091-001 Flash Backed Write Cache FBWC Battery for P420 and P421 654873-001 | eBay