Originally, I was going to try just using some sort of glue to fix the seam, but thought over time it would just crack again.
Because I know how to sew fairly well, I got out a needle and thread and decided to sew the seam. I used a thin needle because I didn't want to split the canvas as I was sewing it, dark brown thread and very small (close together) stitches. I also gave the canvas a good cleaning with baby wipes and removed any marks on the straps with a ME and baby wipes, then conditioned them.
Here is the result!
I also made a stiff cardboard insert that I pop in along the top when I'm storing it, as to reduce the stress along that seam.


