Carve it out of wood or make one out of crafters clay...the hardening kind.
If you're running Cherry Bombs, those are very easy to make!
![](http://streetperformanceexhaust.com/images/cherry-bomb-mufflers.jpg)
For a standard muffler just lay to sections of tubing next to each other. wrap with foil tape...fill in the ends with putty.
![](http://ecx.images-amazon.com/images/I/31bjd9FJY5L._SL500_AA300_.jpg)
A piece of oval shaped wood, such as that found inside the bottom of a roll up window blind. The bottom or pull end of these cheap window blinds often have a piece of wooden (oval shaped) dowel in them.
![](http://www.get-home-improvement.com/images/get-home/window-shade.jpg)
To be a modeler you have to be part artist, detective and engineer.