I remember going one year as a Cylon and another as Boba Fett. The masks would be flimsy with an elastic string. I think the costumes were one piece made of really thin plastic or vinyl or something.
The Haunted Closet: Let's Go Halloween Costume Shopping!
Scroll about one third of the way down! They also made R2D2, and the robot from the Black Hole and Twiki!
And further down, Warduke! Shogun Warriors! Evil Kneivel! etc....