DIY Cap Door?

Looking for anyone who's tried it or has any other ideas.

When I bought my 02 XtraCab it came with an A.R.E. MX cap, but was missing the swing up rear window (above the tailgate). New price is coming in around $320 for the door. I've called around to scrap yards and used cap sellers in the area, but have had zero luck.

...so, anyone have any thoughts or experience making your own? I'd think plexiglass would be easiest to work with. I'm no stranger to making things, so i'm not worried about tools or ability, it's more the: can it be done, what dumb thing did i not think of that's going to make this a fool's-errand.

Make the whole thing out of thick plexiglass, or make a frame for it? If so, any thoughts on what to make it out of?

or maybe it's a good idea. or maybe you know someone with a messed up cap who wants to make a little extra cash by pulling off the window.