Heater Firewall Gasket, Retainer ??

does anyone know where I can get the metal ring that holds the gasket in place which seals the hole between the firewall and the heater blower motor. My truck is a '53 3100 with the "deluxe" heater. I found the gasket at chevy's of the 40's now I just need that darn ring.

 

this thing

here is a stolen and doodled on pic that may help explain what I need