Sunbrella is what we use for golf cart enclosures where I live. Is that too heavy? Not sure if it is waterproof or water repellent. It’s very durable. Comes in many colors and patterns.

https://www.sunbrella.com/browse-fabrics/fabrics-by-use/all-fabrics

When I Google parachute fabric there are lots of websites to purchase and maybe you can even get it at a local fabric store like JoAnne’s fabrics. Here’s one website. https://www.chicagocanvas.com/product/rip-stop-nylon/

It’s called “plastic sheeting.” Contact a building supply center.

Try Dyneema® it is made by DSM about 35 miles from where I live.

Call around to sailmakers (there are a few in your area) and ask them about this. Most of those folks love to chat about such things, and can probably give you some good tips and advice. Google “sail makers in upstate NY” to get started. Sounds like you’re looking for something that would make either spinnakers or light weather sails.

These are great Ideas! Good places to start.
I’m guessing I will need something special but this is helpful.

Dyneema is basically Spectra fiber under a different name. I think it is the highest end sail material out there these days.