Black shop vac hose?
Is that just black adhesive vinyl brother?Go to any crafts store and get black vinyl wrapping. its very thin and adds no extra girth, unless you're into that kind of thing
Costs a couple bucks for a small roll, self adhesive, and looks stock. I have 3" fork extensions and use it to cover up the line. Don't have any close-ups, but you can see it looks like it came with the bike.