I think of fiberglass as plastic, so you might want to check out "sun screen" which is a fabric type of material it can be cut with scissors, although I have not tried to sew it on my machine I think it would be sewable on any machine. It feels like fabric, soft and durable. You might want to check with a glass company and see if they have it and you could purchase a small amount and see how it sews on your machine before you invest in a lot. Hardware stores may have it also in the window screen department.
Just a thought there.