The large portlights in the main salon are a royal pain to replace/repair. The glass is curved to match the sides of the cabin top so it is difficult to find a drop in replacement.
Actually, the glass isn't curved, the frame bends the glass to shape. When you remove the glass from the frame it will be flat. It's not hard to get replacements made, just be sure to get tempered glass or it will break when you put it back into the frame.