A little know, but awesome place to get party supplies and costumes is the Secret Attic in New Berlin. They have hard to find party supplies for themes like Sweet 16 and Over the Hill along with some neat toys and knicknacks for gifts. When you are in a pinch and need a costume they have costume sales and rentals. The couple that owns the Secret Attic are very helpful and always available. Sign up for their mailing list and receive valuable discounts each month.