A section from the "drop" portion of a steel, bicycle "drop-bar"
handlebar is actually already bent into the same shape as a
stock Express exhaust header.
Obviously, it does not bear a mounting flange like the stock
pipe, but these handlebars - from ten speeds - actually have a
slightly larger inside diameter.
I sat down to make myself an exhaust header for a pipe
experiment, and expected to spend hours at it. Fifteen minutes
later, I had a header finished and tacked to a flange.