I ordered some of this bellows material from McMaster and was pleased with it....
McMaster-Carr
Item #
1320K34
It's a woven nylon material that's slightly stiff. If collapses well (better than the stock rubber) and is a decent replacement. You can cut it with scissors but it's held up fine on my X2.
That being said... I'd want a better sealed environment on a CNC machine if possible.
I'll be interested in what you come up with.
Have you given much thought to the coolant systems? Mist, flood etc? (Edit: LOL, never mind... went back to page 1 of the thread and said 'Doh! Flood it is... )