I was looking for Star Wars costumes on the web that I can buy online.
I search for a while using the keys "Star Wars costumes" and switched to images search in the Google's search pages.
I must say that there are many companies and designers creating costumes for Star Wars for kids and adults.
If you are looking for a female Star Wars costume, I would suggest you to have a look at the Femtroopers armor suit for female Stormtroopers by Sith Vixen. Although I liked the costumes for femtroopers, do not forget that femtroopers are not a character in the Star Wars universe. Since all the troopers are clones of Jango Fett, they are all males. So there are not female Troopers in the Star Wars Galaxy or in the Star Wars movies.
You can refer to Sith Vixen site Femtrooper pages
for female Star Wars costumes.