http://www.quartz.saint-gobain.com/MICAVER®.aspx
This looks like an interesting material for this application.
Sounds like a polyimide or other non-outgassing polymerizable organic and ceramic composite could be a good choice giving stiffness and robustness against shock.
The part could be coated by SiO2, AlN, etc. by sputtering or other deposition technique if no organic exposure is allowable.
