I was thinking about making a Vault Suit for Halloween. I found it amazingly difficult to find cheap, classic jumpsuits for sale. I've only seen them in a store once, I wish I had gotten a few of them now.
If you're looking for cheap, check out Rubies costumes, I got a TNG costume, complete with resin commbadge and metal pips for about $40 from them. Unfortunately I lost the link to the site I bought it from, but they had a wide selection of uniforms from TOS, Trek 2009, TNG and DS9. The one I got isn't quite TV quality, but it's not bad, it zips up the back like the real thing (the old 90s ones were pull-over style). The fabric is not canon, but it looks good and it's breathable (another problem with the old costumes)
If you want something more professional quality, and are willing to spend time on it, Roddenberry.com sells canon uniform patterns for about $20-40 each piece, that doesn't include fabric, but it's probably cheaper than Shadowdale.