There once was a Door made of plastic that was sold by a lot of After Market Parts Stores, not sure if it is available now.
The door was flat so I do not think it would be hard to make.
The door was held shut with HD Velcro and it had a hole in it to open it.
The Hinge might be a problem but it was a light duty Piano type of hinge running almost the full width.
I had the door on my 88, the hole always bothered me, worked well, only had smaller items in it but it covered the hole.
Luck on the hunt… take some diamond plate or std 1/16” Aluminum, maybe even plastic and cut one out.
Use HD two sided sticky tape to mount the hinge to the plastic and as said HD Velcro to latch it up.
4x4, 5sp, Std Cab, Stepside, E4 Red
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