There was a recent discussion about such caps on the militaria forum and I think we've touched on them here. Here is a perfect example of an early repro. For some reason, despite the extensive use of plastic instead of leather, these fool a lot of collectors. The trip is plastic and the visor is some weird synthetic thing. Horrible. I bought one online before Ebay was big and promptly returned it. You can see by the shirt this is a thrown together "set".
http://www.ebay.com/itm/WW2-US-Army...078?pt=LH_DefaultDomain_0&hash=item2327d77d36
http://www.ebay.com/itm/WW2-US-Army...078?pt=LH_DefaultDomain_0&hash=item2327d77d36