My F 150s had hard covers, the 99 was fiberglass, the 20 is some hard plastic type stuff. Should be able to find a used one at a salvage yard.
'bout 10 years ago, a guy down the street made one, 2 sheets of 1/2 ext. ply. Ran the 8' length width wise cut to about 4+ foot something/5'. Left over pieces went the other direction underneath the top layer, glued screwed. It laid in an aluminum frame on the bed rails and got hardware from Lowes.
Then he smeared glue on the entire top and upholstered it with outdoor vinal. Put on two gas struts and done!
He rounded the ends of the aluminum angle at the back, looked pretty good up close and when he passed by it looked like a nice factory job from someplace.
Bet he had less than $200 in the whole thing. His was about the same weight as my fiberglass cover.
If it had been mine, I'd probably fill the butt joint on the two pieces and use bed liner over the top, paint the underneath side. But the vinal did look nice.
Long ago, like 20 years ago, saw an aluminum cover the lifted 3 ways, hinged on a center hard section with both side lifted up from either side, then close those lids and the whole thing lifted from the rear. That would be very handy getting stuff up near the cab from either side. This was on a work truck. I've seen others that opened from the sides that had tool boxes below the side hatches, but I don't thing the lifted from the rear.