First: your strap that holds the sword & sheath is going to need to be anchored to your waist belt, otherwise it's going to slide down & be annoying. (can't rely on designers to be accurate to real world physics). I'd do a small lobster clasp and loop or D ring, easy to put on and remove the sword as desired.
To attach the sheath to the leather shoulder strap: Chicago Screws; cheap, easy to use, can be assembled & separated as many times as you desire. https://www.tandyleather.com/en/sear...icago%20screws
Last is the fabric wrapping, but I admit I'm at a loss. The art you linked looks like a leather sheath, wet form type as it's smooth and shows 'stitching' down the center. I would cover it with a leather look vinyl, and use rubber cement as it's the best glue between those two materials. YMMV