I need to replace the rubber door bumpers on my 32 coupe. being Plymouth I haven't found any aftermarket parts. I have done some research and I should be able to cast them in a silicone mold. I do have one original I can use to make a silicone mold. but finding a source for rubber or urethane in black of the correct hardness for making the actual part is a bit complicated . can someone suggest a product that would be suitable for making these parts ?