We struggled with this too with two windows. We finally bought custom drapes. The main problem was the light that would come through from the sides of each shade. I image that if you can attach them within the window casing from the top( if that’s even possible) you might be able to minimize this. We did get a roller shade that was big enough to cover French doors… but the door frame blocks that gap and less light gets in. Good luck!

Pictures of your window may help…to get more suggestions

There are some brands of black out roller shades that come wider than that. I think I've seen 119" and even 121". I think they were by Hunter Douglas and Graber. You'd need to contact a custom window fashions dealer. A professional designer would be able to steer you in the right direction.