Print two eye pieces and two caps. For the lenses, put an eye piece face down on a clear piece of plastic and trace around the outside,then cut out the lens. Place the lens into the inside of the cap, then screw onto the eye piece.
For the head straps, melt the ends of paracord and smoosh flat so they are bigger than the outside holes. You can alternatively just tie a knot on the inside.
For the nose bridge, I used two pieces of 1.75mm filament cut to be about 1cm longer than the distance between the eye cups when you wear them. Put the filament through the nose-side holes and carefully melt the ends into spherical blobs so they won't go through the holes. Alternatively just use regular string, or similar.
See the photos to get a sense of how I made the head strap and nose bridge.