Some seriously cool (and a few really goofy) looking alt. costumes people designed for a 'redesign Captain America' contest. Well worth a look, and might provide some inspiration for customs. The Derek Toye and Shane McDermott entries I think would make great action figures.
Oh my god my love for that winning costume can't be described. I've been trying to hard to find a costume that would be easily constructed. That uniform is just... awesome. I love the utilitarian nature of it, the layered look, the gear and boots. My only qualm is I'm not digging the gloves too much.
I have seen Captain America adult costume almost anywhere in ebay. LOl. I also saw his damsel in distress costume, so that was a nice pair up for a party! Cooooooolll!