there are places that stock reproductions of these clothes but the can be pricey. search military reenactment costumes and you'll see some of them.
i've always had good luck with army navy stores, many of which are now online if not in your town. also try craigslist and ebay. better deals on craigslist but finding something specific is easier on ebay.
also garage sales and flea markets.
i just scored a full air force dress uniform with hat belt and shoes for 5 bucks at a garage sale and the lady threw in a bag of old fatigues for free.
unfortunately they were circa 80's or i'd send em' to ya.
thanks
-k-