hello ken,
have you thought of flat fibreglass as used in printed circuit boards, it is very easy to work adis very strong. I used to work with it for a living and use it for all sorts of things on my boats, and I seem to remember that there a couple of firms in wales that made pcb,s and I am sure that if you asked them on bended knee, you might get a few offcuts, hope this helps and good luck.
yours ron