I had such a requirement previously which I solved by taking a SWB full hard top, splitting it longitudinally & piecing in a section of alloy to fill the gap. This was sealed with silicone & pop rivets. I fitted hinges @ the front so the lid lifted @ the rear making access easy with suitable padlock hasps to secure the lid & keep the attractive items out of sight (tools etc!). I used a series hard top but you might manage to adapt a ninety top to suit.. If you are lucky you might find 2 roofs to keep the profile matching but it seem like a waste of a good roof.
