A yellow or black raincoat.
Plastic Firemans hat from costume shop.
Refelctive tape- Optional.

Do you have a yellow or black raincoat? All you need to do is put red reflective tape on it around the sleeves while it is dry. Using black electricians tape put a large number on the back of the raincoat. Purchase an inexpensive firemans hat and your done. You can cary around a red fire bucket to collect your candy in.
Maybe a friend or family member is a fireman and can let you borrow an official raincoat and helmet.