Sliding Rear Window

[Mopardik]

I just recently received my new rubber for my rear window, and before I R+R this thing, I figured I would at least ask if there is any place that has a sliding rear window for a '69 D300?
I searched and found a few very old threads about them, but they didn't really provide too much info.
Some of those threads also talked about possibly using one for a 67-72 GMC?
Anyone have a line on an old one, or know if this swap works?
Thanks.

[PwrWgnDrvr]

In decades past I have pulled 2 from junkyard trucks. Both were sold long ago, but I do remember one of them had black plexiglass pop riveted to the frame to make a filler that fit the opening exactly. It was not a large filler - about an inch at the wide point tapering to zero at the ends.

[Mopardik]

Hmm, I'm wondering if that modded one may be the GMC fitment I read about? In those old threads someone had mentioned a window he had being super close, but slightly off in those areas. Perhaps someone else tried out that "solution" that you came across? Intriguing, especially since finding one of those older aftermarket ones will be next to impossible. Since I'm not at all worried about absolute correctness, and am almost embracing the semi shade tree plan on this ol' truck, I may just roll the dice and go for it. Do I feel lucky?
Thanks for the help (again) PwrWgnDriver!