Heater tube gasket plate

Hi,
I am working on a 72 Demon. I seem to be missing a small flat metal plate which fits over the two heater tubes as they come through the firewall. The plate has one screw hole which is located between the two tubes. Its function is to hold a foam gasket in place so no water will get through the firewall into the passenger compartment. Obviously there are also two holes drilled in it for the heater tubes to pass through. Anybody got an extra one they want to sell? Thanks.....