I've just done a quick Google on translucent fibreglass panelling and found some, but only uk firms. These days it tends to be called GRP (glass-reinforced plastic) or FRP (fibre-reinforced plastic. I'm pasting a link to an article that describes it so you can check whether it's the same...
My PVC panels would have lasted better had I not piled them up on a warm day in Spring. I can't recall now why I didn't put them away properly but I took them off in a rush because the weather suddenly got warm.
When I went back a couple of days later to stack them properly, those in the middle...