It costs a ton of money to have a large custom bellows made, and quite a bit of intensive labor to make one. Why not use existing industrial plastic rubber bellows and flex/corrugated duct? There's a neat little corrugated bellows on the very same computer chair I'm sitting in to type this, being used as a dust cover for the back. These type of objects are all around us. I'm surprised people don't go this route. Just a quick google search came up w/ these two. There must be literally hundreds of suppliers out there. Maybe even Home Depot or Lowes would have something.