Being over here in the UK (although I havent commited to building anything yet!) i've not found anywhere that sells waterproof hinges - except piano hinges with a rubber weatherstrip that coach builders use.
Today, ripping a roller shutter door to pieces at work I kept a few of the old 'Latts' for experimenting with. With a bit of pressing & cutting they'll probably do the job - galvanised as well.
More as it happens...
