Doubling voltage of two 9V batteries in series? [OR high voltage]

ok..
Erm, while we are on the same subject, would it be possible to construct a very high voltage capacitor charger (about 400V) with 9V batteries as the power source? Camera capacitor chargers do this but is it possible to build them out of discrete components? (for a reasonable price)

PS> Yes..I'm trying to build a coil gun XD and disposable cameras aren't available where I live.