cheap and easy - buy some silly putty - make a small cardboard box (3" x 3" x 1/2"). Place the silly puty in the mold box and level smooth. Gently press the original part into the silly putty. Gently remove. Pour in the resin, epoxy (or whatever you are using for the casting material). Allow to cure. Remove the part. Make a few copies. Trim and replace the damaged part. Post pics of your results.
Also - Scale Auto # 89 - Feb - 1994 - page 54 - Promo Rescue - repairs.
If you do not have this mag, I can post pics of the pages.