Having designed power supplies and battery chargers for a living, I'll give you my input on this. There are 2 basic types of DC power supplies - switching and linear. Linear supplies are simple but require an iron core transformer. A transformer for 200 amps would not be off-the-shelf, it'd have to be custom made. It'll also need a hand truck to carry. Switching supplies are smaller and lighter but at that power level building one would be expert level electronics. And you still need a custom made high power torroidal transformer.
So, my advice is keep your eyes open on
eBay. But remember that 2500 watts of 14V is gonna be a heavy item to ship.
Edit: Just an idea - if you're mechanically able.. a 200 amp car alternator driven by a 220 V AC motor? Lessee.. 746 watts per hp means you need about a 3.3 hp motor. Just throwin' out ideas..