Had a similar problem to the OP. Strong cross wind, single carriageway, doing about 180 kph, 18 wheeler passing in the other direction, heavy turbulence and crack, windscreen flops down.
It’s a 2010 windscreen with slight modifications in that I drilled extra holes to raise it about 2 inches and fitted an MRA spoiler on the top - see pic. It is not a drastic change to the original and it wasn’t even fully up when it happened, so just a bad set of circumstances.
On arriving home, opened it up and found the bracket had broken – see pic - Windscreen bracket with broken piece” (pic courtesy of the Australian forum). I wasn’t so lucky, the broken off piece was long gone together with the Teflon guide.
Priced a replacement but, as all have found, the bracket is not sold separately and only available as a full system at about US $ 700. Not wanting to spend this kind of money decided to find an alternative solution.
Did some searching and found the Australian forum where someone had made an attachment plate with welded stainless steel and reported that this had worked. Not having the facilities to machine and weld stainless, thought about using mild steel angle 75 mm wide and 3 mm thick but with the one side ground down to 5 mm. In order to attach it to the broken bracket, drilled 3 off 5 mm holes through the bracket through the circular sections. (Also drilled a 2 mm hole through the front to strengthen the assembly – more about that later) – see pic “Windscreen bracket repair 2”
Bent the angle iron using a vice, a clamp and 2 pieces of wood to keep the bends true. Found that it needed a cut-out to clear the lip on the guide plate hence the strange shape. To allow the angle to bend it was slotted and welded after the bending- Finished article pic “Windscreen bracket repair 3.
Need to post some more pics so will carry on in the next post.