I made mine out of a piece of aluminum sign and used JB weld to fasten 4 threaded studs to to the back side that fit in the corners of the control opening. Painted it black to match the dash core.
You'll have as good a chance finding one as anybody since virtually all heater delete cars were sold in hawaii and Florida. I have one from my 67 but it won't be a bargain if I sell it.
Well figured I would just put it out there and see what comes up. Worst case I make my own.
I had also seen something before where someone was re-poping them. Any one know about those?