You probably tried this already, but I'll throw it out here anyway.
I searched IMDB.com for the costume designer for "The Santa Clause." It's Carol Ramsey. Here's her page
provides contact information for Ramsey's agent. You might be able to get in touch with Ramsey through the agent to ask whether that sweater might be available somehow. You never know! Suggest to her that she could make a fortune with a line of tasteful, non-ugly Christmas sweaters.
Good luck, and let us know what happens!