That is going to be a tough one to find--best shot at it would be finding a whole exhaust manifold someone kept after de-smogging an engine,that still has one on it..and around here if any exist they'll be buried in someone's garage pile of parts or at a swap meet--those tin heat stoves rusted away pretty fast around here...
If anyone makes them aftermarket I'm not aware of it..
I had a truck that was cold blooded and the carb iced up in the winter without the "stove" pre-heating the air coming into the air cleaner..
I jerry rigged a crude stove up by using a metal stud they use in construction for drywall,I put two pieces together about 8" long, and closed one end facing the rear of the manifold,left the front facing end open..
The metal studs have a hole in them that was the right size for that crinkle tube that goes to the air cleaner..it wasn't pretty but it did the job..
I've seen other guys make one out of a tin can sliced in half and the ends carved out to fit around the manifold,and they used wire or pop rivets to hold the two halves to the manifold..some years back we had to pass a visual emission inspection,until they decided to drop that requirement for vehicles over a certain age,and any parts like smog pumps and manifolds with the A.I.R. pipes,the brackets,etc, that a lot of people removed, were suddenly in high demand,and hard to find.
