Best bet might be a layer of thin SS; backed up with a insulating material such as Koolmat, or a couple layers of Al foil on the cool side.  For really close to the hottest part of the exhaust; Koolmat makes a multifoil inconel mat that should be good to close to 2000F.  Of course it is expensive.

Al

 

Thanks for the Koolmat pointer.  The inconel stuff you mentioned is good for 2500 degrees, and (only <g>) costs $1.00 per square inch.  Even at that price, it might be just the ticket for one engine mount tube, and a small area of cowl next to the exhaust pipes.