The501stlegion is kinda like the elite costuming club for all things star wars each costume has list of requirements so that it is screen accurate you can join once you can apply for approval after you have completed a costume to their standards this link is for the esb boba just to give you an idea
Costuming:BH Boba Fett-ESB - Databank
If you are looking to just get the bottom half of the flight suit im sure some of the people on here would be willing to do something "custom" for you also MOW (man of war studios) does two piece flight suits you could ask him if you could get a hold of just the bottom half