Well, you can call up the makers and find the closest distributer, whom will usually will cut it to the length you want. That's one part done.
Then, you can email elemental Designs (eD), who do custom woodwork. MKtheater had them make a whole bunch of them for his epic sealed setup, and he said that their prices are really quite reasonable. All he had to do was mount the driver to the baseplate, slide the assembly into place in the tube, and wait for the glue to dry. About as easy as you can make it!