If it's only the hatch portion you are wanting to replace, you could get a fabrication shop to make one out of .060 or .090 aluminum. The middle crank bar from the existing hatch could then be spot welded or riveted on the new top.
2015 Ram 3500 4x4 Crew Cab SRW 6.4 Hemi LB 3.73 (12.4 hand calc avg mpg after 92,000 miles with camper)
2004 Lance 815 (prev: 2004 FW 35'; 1994 TT 30'; Tents)