First I measured the original case and of course thought about the length of my (metal) zip:-)
After some planning I sewed both unzipped halves face to face with the canvas.
I folded the black fabric and sewed along the zip.
I closed the zipper and sewed the shorter edges. On this side I added a small square folded in the middle to hide a small hole after the end of the zip. On the other one, naturally, I let the fastener a bit open when sewing :-)
Zig-zagging and some final editing ... tadaaaa, here it is:-)
I wanted to make this one also from another reason - I can decorate it myself with some infantile broidery. If you heard something about crazy quilting.. :-D