You might be able to find replicas of the theatrical outfit from 'A Christmas Story' in some specialized costume shops. They often stock outfits from popular movies.
Well, for the theatrical outfit from 'A Christmas Story', you could start by checking with large costume rental places. They usually have a wide variety of costumes from different movies and shows. Another option is to look at fan - made websites or forums dedicated to the movie. Sometimes, fans create and sell their own versions of the outfits. You could also try looking at vintage clothing stores as the outfit has an old - fashioned style and there's a chance you might find something similar there.