Greetings:

I have replaced them with 100mm lengths of 5mm thick
perspex (that's Plexiglass for those divided by our common
language) cut from a large piece that I picked up at the Puckeridge
LF site.

When things started burning up here, two of the things I tried were
plexiglass and also a plastic insulator I cut from 3 cm orange natural gas
pipeline plastic.  Both burned through within a minute or two.  I had to got
actual ceramic insulator before the fun and games stopped.

Larry
VA3LK