Although the shows I have been associated with have generally been based on scripts custom written either by or for the production company (and here's how to create your own), many people have been asking me lately where they might find commercially available, ready-made scripts.

So far, there haven't been many that I have seen published, but you may be able to find a suitable script for your occasion at one of the usual sources of plays for production:

• Contemporary Drama Service (Lists a few mystery plays written for interactive theater)
• Bakers Plays (Primarily serves the school and church market)
• Samuel French (Handles plays and rights for many of the big names)
• AreYouGame.com
  (Games for adults including mystery party packages)