If you just want to stop the rattle and wind whistle (roar), go to the u pull it and get some window surround channel, felt, stuff. There will be enough to fix both sides divider with the channel from 1 side, but get extra.
On my mj and the xj, the divider was hard, like plastic. But where it entered the bottom of the window opening height (Bottom of window opening) it was in better shape.
The channel from the top to this point was brittle, and I pried and chiseled it out.
The side window opening stuff IS slightly wider, but with a little experimenting I trimmed the top to a slight angle, and left it just slightly long, and worked it in place, to butt against the remains of the lower channel. A little soapy water or just plain dish soap straight, will help.
The extra width sort of pushes the seal lips tighter.
Best part of this is that the upull I go to didn't even charge me for a handfull of window seals when I was getting some other stuff.
The side window one has an extra lip for style, to cover the pinch weld, but doesn't interfere with the operation, I just left it, on the inside of the divider bar.
Try it with your stock window opening seal, there is enough to pull it out of place, and tuck it into the divider without harming it, just to see if it works. It does.
A trucker friend says his Peterbuilt has similar looking stuff, and the dealer stocks it, sells for about $15 for 8 ft. Might work, not verified. Take sample.
I am a cheap bastard and went with what I had, and now ride in damn near silence ... if that is possible in an old mj.