Replacement protective coating for front of rear guards

[7folly]

The front of the rear guards of my Leitch is covered with some sort of rubberised material to protect it from stones. Over time it's become worn down and now the fibreglass is exposed at the bottom. Does anybody know what the material might be, where to get it and how to refresh/replace it? Alternative solutions are welcome. I'll contact Barry Leitch, but it may have been put on by the original builder.
Regards,
Ken.