@groucho Hi, good day.
Sorry for the late reply.
The outside layer is made of glass, you can use some soft microfiber materials to clean the lens, but please don't wipe it hard, and don't do it too often.
Sorry to say we currently don't have any lens cover available, but you can put it in the carry case if you don't use it, and prevent it from falling.
Also, you can join our Facebook for daily discussion, customers might share their using experience there. .
Mogo group: https://www.facebook.com/groups/397245941024735/
Halo group: https://www.facebook.com/groups/429334661330396/
Youtube channel: https://www.youtube.com/channel/UCcSyKAcYUZLmGcLSIM4M_4Q/videos?view_as=subscriber