you don't need a custom / dedicated 'stinger cover', if such even exists. just a good proper sized one. any cover used outside must cinch down snuggly to avoid flapping in wind and admitting dirt / dust.
when I first got my stinger I bought a car cover for a hundred bucks at o'reilly. took it back the next day as a waste of money since we have a carport that faces the right way, north, which reduces the most pernicious weathering element, strong sunlight.
my reasoning for not covering the car was exactly what you mention to avoid, scratching the exterior over time. It wouldn't be an issue right away. but after putting the cover on and removing it a bunch of times, the inside of the cover is going to pick up grit from the car and then scrape it later.
the only possible solution to avoiding this is two-part, wash the car thoroughly before putting the cover on, and replacing the cover before it gets too impregnated by dust and other grit. how practical is either in the real world? I can see a cover being a good idea if you are going to store the car, either inside or out, for a while, say, a week or more at a time between drives. you give the car a good bath and get the cover on immediately after. but a daily driver couldn't be properly covered daily. and how often are you going to replace a cover to keep the inside of it clean? expensive!
