I've never seen a metal half cab for a 76-86 CJ, but they were quite common on early CJ5's and CJ6's. A fiberglass Scrambler 1/2 top would work with your 80 CJ5's windshield frame, but you would have to figure out a bulkhead to seal it to on the bottom and the roll bar might interfere and need to be moved back or replaced. You could use an early metal cab if you changed your windshield frame to the early CJ version.
74 CJ5 complete frame off restoration
82 CJ8 Scrambler Laredo. 4.6L stroker AX15 D300.