Wedding Dress Question?

I want to try on the Blue by Enzoani Dayton Wedding Dress in a size 18 to see how I look becuase I am not skinny and don't want to look like a fool on my wedding day. But everywhere I call about this dress they only have a size 10 as a sample and can't order a size 18 for to try. How can I purchase something I haven't tried on? They expect you to order it blindly. I am starting to feel really down becuase I fell in love with the dress when I saw and wanted to try it but I can't cuz no one has it in a 18 and if I want to try it I have to buy/order it. What should I do? I've called a few places where they have it and every one says "Sorry can't help you". How do they expect you to buy something you havent tried on to see if you like it?