We purchased a muffler from Colin for $20.

The muffler is a racing type so it goes behind the frame and sticks out the back. It is a high muffler so it goes on top of the motor instead of underneath it. The muffler is a little rusty so we have to leave it overnight with some "liquid wrench" to disconnect the muffler from the head pipe. We will look tomorrow to see if the muffler and head pipe are any easier to disconnect.