Hi
I hesitate to suggest the following in fear of being ridiculed. While
this is not "marine" you might consider: hay tarps.

If you are close to any area that is still relatively free form Mc
Mansions and grows alfalfa/hay, farmers bail there hay and many times
tarp it. The tarps on the west coast are extremely durable, reasonably
light and easy on the hand, totally UV resistant and about half the
price of "sunbrella" type products. I guess the poor farmers can
not afford expensive marine grade protection. The hay tarps can be
custom sized.

When I was talking to the farmer, tarp was a low priority project on my
list so I did no get any address details but the sruff looked great.
Forgot the actual price but did remember it was ½ the price of
sunbrella stuff.

Blue Wal-Mart tarps............. too noisy! I prefer the soothing
flop-flop sound.

How about old sail cloth? Or buy new scraps by the pound. Practice
sewing it together like a quilt. Great practice and you get a tarp at
the end.
Bob