I have only ever made one that might be called a Howdah Pistol by some, but I am not sure if it would truly qualify. I am not sure how specific that term is.
What I made was a single barreled 8 bore pistol with a 1-25" twist on a reinforced piece of rosewood for a stock. It was a very intimidating looking piece. 8" long barrel.

I bet it would have cleaned a tiger off an elephant quite well, so I called it a "Howdah" but I am unsure if and real Howdah pistols of the 1800s were singles or not.