your 100% correct, you should just make one yourself, because it really is as simple as you explained it.
That is if you have a lathe , a taper bar or a cnc or some way of tapering the shaft.
The boring bar or tap to make the threads in the shaft the dust control system,
a shop garage or spare bedroom to put all this stuff in.
A way to design and cut the strips of wood in pie shaped pieces or i guess you could laminate flat piece of wood together like meucci or you could core the solid maple dowel and stuff graphite rod in there or silicone or foam or balsa wood.
So add a gun drill in and a good table and band saw a big air compressor in too.
Don't forget the trial and errors of which glues to use and warping problems laminates de-bonding, weak tenons and ferrules splitting.