Low tech solution proposal:
MacGyver your existing slide cover by drilling a hole in it where the camera lens is, and covering that with Scotch Magic tape or anything else handy that is translucent, but not transparent.
Or if you have access to a 3D printer (I’m happy to help) This cover could be printed (more smoothly than the designer did!) in translucent natural PLA: https://www.thingiverse.com/thing:2814505