I used breathable camping groundsheet. Easy to cut and does not fray. It is relatively cheap, easy to get hold off and as it is an open construction water just passes through it so it dries rapidly. Does not need cleaning just up pop it, shake it out and sweep the deck underneath

It was fixed down with poppers in each corner and it meant I could have a separate section over the engine hatch easing access

I intended it as a temporary solution but it has seen one good years use and seems to be wearing well