Do you live anywhere near the South Western US desert?
I had a hippie friend who used to make them out of fruiting Agave Cactus & sell them in a small artsy-fartsy towns in the mountains.
When an Agave gets old enough, they grow a tall tube up into the air, from 4 to 8 feet high & the seeds fall from it after drying.
My pal used to cut down the tube after they would die & cut it in half, then hollow it out, lacquer the insides & glue the tube back together & lacquer the outside of it to a finish.
Not really difficult at all.
You can tune it by cutting/filing it to raise the pitch. He had a van full of them, cut to resonate at all the different notes.
He made me a great 7' long one in the key of E, to go with most rock & popular music, back when I was in a band.
I can play it pretty good, but I never really perfected the circular breathing thing...bad sinuses.
Here's a pic:
WS