I cracked mine in what sounds like the same spot while doing maintenance last winter.
I ended up using this:
https://www.amazon.com/gp/product/B001DZDCNS/
It has held up very well and does a great job at sealing out water & wind, but it is a very visibly a patch.
Also - it's pretty cloudy, which doesn't bother me since my patch is along the side of the window.