All the piping and the 2 elbows you see in the picture above posted by Tom Chilton where purchased at my local Ace Hardware store. I had to cut slits in the outer layer of the double walled pipe to clamp around the FE pipe. The hose clamps are not sufficient, a "T" clamp, used for marine exhaust, is, but it seems to be okay for the mean time. I don't move the unit so probably I won't need the more expensive "T" clamp. Then I used stove pipe cement to seal it.
I recall that the male end of the single walled pipe would fit inside the FE pipe but then you're installing the pipe backwards so when you get ready to install the cap it is the wrong gender! And...if there is a rain issue, rain will enter the intersections because it is all backwards. Go figure!
The 2 sections of double walled pipe, a total of 8 feet, the 2 rotating elbows and a cap ran about $100. For the same in single wall it would have been about $35!
I had a device on my sailboat for my diesel heater known as a rotating Charlie Noble. It is a vent cap that sort of looks like a wind vane. This may be an answer. I have found one at the following link, it fits a 3 inch pipe, but perhaps you could ask this
marine supplier where they get them from or perhaps you could have one built, or build one yoursel! They can be a bit noisy as they rotate.
The diesel heater has a rather slow flame which I would think is quite a bit more sensitive than the CS/FE.
Peter