One of the US 640 regulars posted up in thumpers recently with some pics of some aftermarket high capacity radiators they had just got for a good price, might be worth looking into if that bent one isn't fixable. I'll have a poke around & try & find the thread.
Edit, found it, ASI rads & hoses: http://www.advrider.com/forums/showp...7&postcount=38
They sell ASI stuff in NZ I think, so ask around locally. It might end up cheaper to import though.