Hi there,
I am not from US, but I have good experience in real sculpture. What I can offer a relief in clay, can can be turned into silicone mold. This mold can be easy transferred to US with no worries of being broken. However other materials that can be used are: artificial marble, (reinforced) gypsum, resign, terracotta. If you are interested, you are welcome to find work samples, and testimonials on my profile.
Optionally a digital sculpt, can be made, to be used in 3d printers, or other CPU controlled machines.
Kindly, Valkan Pavlov.