John,

More than likely the material you are looking for is the cotton/poly
fleece that they make sweatshirts and sweatpants from. It's a knit
fabric with stretch in both directions. I have one that the previous
owner made for my glider. Not sure what you have, but I'd be willing
to send you my old one for the cost of shipping. It fits the ASW19/20/
Pegasus aircraft. It's pretty stretchy so it might fit other types as
well.

I now have a platinum canopy cap that I use to keep the cockpit cool,
and a Ridge sewing cover for when I tie it out. That is really the
best system. But it took me a few years of saving up to change over to
that.

-Kevin