I WAS trying to be serious and offer help. It's easy to build to build exhaust systems. Cans, mufflers, and expansion chambers. It can be as easy as you want to make it. Heck, two sheets of steel cut to the right pattern, welded around the perimeter and blown into shape with a pressure washer. The pie cuts for the header are the hardest part. All in a quality custom tuned expansion pipe wth header can take as little as an hour. Believe me. I know.
I see your point about possible availability . Howevr they also built thousands of the old three cylinder two stroke Street bikes. It's relatively commonplace nowadays for owners to reproduce the expansion chambers themselves. Thirty or fourty five minutes measuring and crunching numbers and an hour or two of welding, cutting and a little more welding and these guys have saved thousands. However I don't see the pipe you're looking for costing anywhere near that.
Hell, I built the expansion chambers on all my two sroke bikes. Even sold a couple pipes.to friends for good $$$
As for destructing one for measurements, I am sure some ....let's say lesser inteligent person..has already done that.