Keystone Electronics has threaded ceramic spacers in 1/4", 3/8", 1/2",
and 3/4" outside diameters, with either 6-32 or 1/4-20 threads.
Digi-Key and Mouser stock some of them in small quantities - roughly
$3 to $6 or so, quantity 1.
http://www.keyelco.com/category.cfm/Standoffs-Round-Ceramic/Commercial-Ceramic-Threaded-Standoffs/p/506/id/1078
McMaster-Carr sells ceramic bars, sheets, rods, etc, but they can be
uncheap. You'd also have to cut or machine them into what you want,
which may be non-trivial.
http://www.mcmaster.com/#Ceramic-Sheets
http://www.mcmaster.com/#Standard-Ceramic-Rods
http://www.mcmaster.com/#Ceramic-Hollow-Rods
You might be able to find something that would work inside a similar
heating appliance, from the thrift store or equal.
Standard disclaimers apply: I don't get money or other consideration
from any companies mentioned.
Matt Roberds