I saw this when I was shopping for gadgets for my cat, and it reminded me of the dog mat on Japanese Fit site. Since the black fabric of Fit tend to show every strand of pet hair, this product maybe just what you are looking for: Back Seat Hammock - TravelingPetProducts.com. Make sure you measure the width of your Fit interior so it will fit.

 

I use a twin size bottom bedsheet, the one with the elastic edges, and I just put it over the whole backseat. It works really well. It stays in one place, I can take it off or put it on really quickly, they're available in all sorts of colors, you can just get flat black if you want, and they're easily washable.

 

I have ordered mine about 6 months ago and I was also worrying about scratches and dog hair (mostly dog hair) but it worked great for me.

Here is the link: https://myspectrumdesign.com/products/car-cover

But Chewy's seat cover's are also fine as far as I know so you could also check them out!