Heat insualting gasket nessasary? Solex 34 pict 5

Ive just taken my solex 34 pict 5 off due to a gap at rear of flange and found the warp to be in what i assume is a heat insulating gasket?
Question is, is this piece essential? And if so where to buy, or should I make? I can't see them for sale anywhere and this one is in too badder shape to put back in. Any wisdom would be appreciated! Will try to attach a pic of the item in question.
 

Thanks in advance