Exhaust gaskets

The other day I was giving my 1980 400i " the once under" while she was up in the air..to my great supprise, the front-half section of my left side exhaust manifold /header is missing her gasket material. This is the front two ports that are exposed when r/ring the starter..The car is performing perfectly, but I,m am afraid of possible consequences.
thoughts please. Are they readily available, or to I have to cut my own, and of what material. Thank you all so very much in advance. Jacques.

 

Thank you Bruce..what took so long...Jq.