The S400 is discontinued so parts are hard to get, but Serpent has a new car in development that will likely use the same front tower. You need to ask this question in the Serpent S400 thread instead of starting a new thread. A moderator will likely clean this one off very soon. But you will probably find someone who has a tower they can sell you, or they can tell you where the best place is to look.
www.battlefieldraceway.com Racing videos at http://www.youtube.com/snoopyrc