The canopy over our 5 year old swing seat (plastic) has become torn
and irrepairable. I'd like to make up one myself, but I'm looking for
advice as to what type of material to use.

Ideally it would need to be resistant to bleaching in the weather, not
so thick that it couldn't be machine sewn to fit and preferably not
shrink or expand much in the rain.

Any useful suggestions?

As usual, thanks in advance!

Matt