Finding A O Smith Parts

Hello, I have been trouble shooting my FSG 40 213 model propane A O Smith water heater and with the help of my local propane supplier determined that the pilot burner orifice part # 180824 is why the pilot will not stay lit. The top of the orifice was accidentally knocked off while cleaning so it needs to be replaced. Every parts dealer tells me the orifice is no longer available. Help, I do not want to buy a new water heater because of the orifice.