My advice would be to commission it..It'll cost more, but you said your willing to pay if it's worth it, which this way it usually is.
Look at these ads, then when you find people you like their work of, go to the commissioner review forum and look in both review threads and search the forum (paste the commissioners username [if they have a business name try that too] in the search function) for reviews.
Now for the advice on buying online. The main part is talking about this:
Originally Posted by PsychGuy274
Additionally, I haven't seen these costumes on actual models, just on mannequins.
There is a reason for that. Wholesale places (places where you by pre made items from ebay and other sites that are selling already made to ship costumes) that DO have a real person wearing them in their pictures, are actually the ones to avoid..If they have real people wearing a costume n the pics, chances are very high they just took it from google or some random cosplayers gallery.
And you can find reviews on them. Te commissioner review thread (the first one) has a crap ton of the ebay stores with reviews. Look them up by company name, not by username, too.