Night Vision Camera Lens Protection

I've read some old posts on this forum where there is a physical protection screen or something that helps to prevent the night vision camera lens from being damaged. I called the dealer and the parts guy said there is a $60 part that provides protection. He couldn't tell me whether it was a screen or plexiglass. For $60 I'll make something that should provide protection, although I'm not sure if it would affect how the camera works. The camera opening in the grille has vertical bars that are tightly spaced which should provide some help.

Does anyone know if the camera is covered by warranty if a stone hits it (I had heard a rumor that it is for one time)? You'd think Caddy would provide a free stone guard to all users instead of getting into a warranty dispute. Has anyone tried plexiglas or screening? Thanks in advance.