C.W.
Is there a party city near you? That's where we went growing up. I'm not sure what exactly they have but I would think they'd have something like that. I'm not sure about the helmet and costume but they do have costumes there.
http://www.partycity.com/search.do?query=space
They have it on their site so you have to call their local store to see if they have it or can order it. Scroll down and you'll see an astronaut costume for $29
Party City near you
Greenfield Commons
2292 West Indian Trail
Aurora, IL60506
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I'm bored so I just googled it lol