Vitreous carbon tube

To whom it may concern, I have been unsuccessful in finding a manufacturer capable of making the tubes described below in vitreous carbon.
We will probably have to go for pyrolytic graphite coated graphite tubes. Before any final decision is made I was thinking about using ceramic tube maybe boron nitride or Silicon carbide. The tube will see a temperature of about 1550deg C for about 1 minute inside a silica tube as an oxy hydrogen flame traverses along the length, the internal volume of the silica tube is at vacuum.If either material will stand this, is it possible to make the tubes to the tolerances given below or what are you able to make to. As we are a research facility any final order would be small, perhaps two of each item.The specs (all in mm):
OD: 23.90 +/- 0.01 and 33.90 +/- 0.01 (if feasible)
ID: not particular critical, as long as the wall thickness is greater than, 3 (e.g. something in the region 1 to 18 and 1 to 28 respectively would work)
Length: 1000 preferable, 700 or 500 not desirable but acceptable
Straightness (bow): better that 0.1 over the length.
Kind regards
Mark Mason