I've wanted an X-Wing pilot suit for years and finally got all the parts together. To be accepted at conventions like DragonCon your costume must be exactly like those in the movies. That's called being Canon and there is a whole industry of mom and pop fabricators who build the right parts. The costumer's job is to gather and assemble all those parts for the costume in question. And I have a trooping box to carry my costume and gear in.
For Star Wars good guys the gold standard of costuming is the Rebel Legion. My Rebel Legion profile is here. They have lists of what you need for any Star Wars good guy costume and their message boards will point you to the vendors. If you want to be a Star Wars bad guy you'll find the same information at the 501st Legion.