Being that I am completely untalented when it comes to sewing/tailoring etc, I can't help with that.
I'd check google or ebay or something if you're looking to do as little work as possible.
Quick google search I found this - http://www.theirongategallery.com/V-tech-Standard-Issue-Vault-101-Jumpsuit_p_16.html
But with an outdated site and $250 price tag, you're probably better off making one yourself.