I bought one from Wally World for $20. Charges both 12 and 6 Volt and comes with a Two Pin Connector along with the Classic Alligator Clips. Can't beat it for the price! Good Luck..
+ if you have verizon fios tell them your backup battery died they will send you a nice 12v sealed 9ah for free. I just used it for the first time yesterday 7+ hours only lost .75 volts. I use the same charger for the 6v livewell battery.