I'm owner of an acoustic guitar FM700MS, and I lost the saddle... Can someone advice me which size or product I should by? (Probably purchasing from Amazon.ca)

Is there really a ton of difference between these materials as far as tone and sustain goes? I've always thought that nylon was the material of choice for cheap guitars (Like on my old Harmony) but I see that some builders are still using it. I don't know much about plastics, but if I didn't...