Where to buy 12+ volt, 900 - 1000 amp capacitors?

Most online seem to only have the voltage and farad rating and I'm not sure how to determine the amp rating from those values. I just need a 1 second, 240 volt minimum, 900-1000 amp pulse, and was hoping 20 capacitors (each charged by 1 battery) would be a cheaper than buying 20 marine batteries!