First thing first..CAlm down. It's not the end of the world or something..You are getting WAY too over serious here..It's a costume, you will be fine in anything..You will have a fun time in anything..
Now that you are calm (hopefully), look on places like ebay and other sites that sell cosplays. When you look on a site, you already know the site name (like McCostumes, EZCosplay, or something like that), then on ebay, they will have a company name on their photos, as well as a username on ebay to the top right of the ad. Then go here:
and run there name in the forum search. Check all the threads that mention them.
However, you can check both of the review threads to see if there are any there too, just click in the thread and use the same search thing. Look at the reviews. And rather than just seeing the grade given, also read the reviews. See if they are to your liking. Once you find one you like, that should be the one you order from.
For sizing and all that, we can't tell ya, so read the ad and see what they want.