Exhaust leak at the choke stove

I have been trying to get this exhaust leak closed but I have not. On my exhaust where the choke stove is, leaks. I have the cover and I bolt it down but it still blows out. Main issue maybe that I can not find a stock gasket and most materials I use are not good for exhaust (Heat).
What have any of you used that holds?
Did you ever attempt what was suggested by slantsixdan? I have a 70' dodge dart swinger 225 with the same situation. Are there any alternatives other than what was suggested?