OK, the VTK100N is discontinued and the Visiontech no longer carries the replacement part. So I'm going to try to make a new lens cover using plexiglass.
Since the lens cover is about the size of a dime, I'm going to try to use a dime as a template to cut a rough shape. Then using the dime again as a template, I'll use a dremel tool and smooth the edges. I'll let y'all know if it works.