|"Well, I think we should put it back in order for them, don't you?"|
Invisibility Token is an item used to activate an Invisibility cloak.
There is a device, Invisibility Booster, which turns turns the car, its passengers, and everything else inside invisible.
There is also a section of books in Hogwarts Library, the books within this section discuss invisibility and are, appropriately, invisible.
Bimetal alchemical thread was a patented magical fibre, invisible to practitioners of the Dark Arts.