Finding materials on the Web is easy. Find the right material can take more time. Here are some suggestions to give you better results when you are looking for costume materials on the Web. A Google search on the term "costume" for example will give you a lot of commercial sites where you can purchase costumes, but few where you can look at historic costume. If you are getting to many results that are not what you need, try doing an advanced search limiting to .edu or .org sites.
Follow the link and fill in your keyword(s) in the top box, such as "costume" for example.