Certainly see if a pond club in your area can help take some of the fish. If not, you can temporarily keep them in anything non-toxic. That means kiddie pools, plastic storage tubs, stock tanks (cheap, big "ponds"), etc. If you can add aeration or even filtration, they can probably survive in those things for weeks or months until you can build a larger pond. Be sure to cover over any ponds to keep the fish from jumping and predators from getting to them. If these temporary ponds are to be without plants, keep them in the shade. If you can build a pond of around 2000+ gallons, that would be great but they may be able to all survive in 1000 gallons (just the rescued fish, don't know what you already have). If your 600 gallon pond is already stocked up with fish, I wouldn't put the new fish in there but rather hold them in other containers/ponds until you can make something larger or find an alternative home for them.
A MA pond club:
http://www.pioneervalleypondclub.com/