Magic cloaks are a very common trope in many fantasy settings and have been made popular recently by several book series and their movie adaptions such as the famous Harry Potter franchise. Cloaks of invisibility such as Harry’s were standard fare for thieves, rogues and other stealthy types since the earliest days of role-playing.
Perhaps the earliest recognised appearance in recent fantasy literature is Frodo’s elven cloak that inspired the classic cloak of elvenkind mentioned above, but this is almost certainly based in part on the original Tarnkappe (German: “magic cloak”, although often misrepresented as a helmet or Tarnhelm as in Wagner’s Ring Cycle) that is stolen by the hero Siegfired from Alberich the dwarf in the Nibelung Saga.
Although undoubtedly useful, an Invisibility Cloak is perhaps not as well suited as a Redcap magic item, even thought the basic spell used, Veil of Invisibility (ArM5, page 146) is only a PeIm Level 20 spell. Invisible characters still cast shadows, make noise, and leave footprints – but more importantly invisibility is relatively unsubtle and marks the wearer as plainly a user of magic as opposed to more subtle effects that can assist a traveling Redcap which are less likely to draw the suspicion of mundanes.
Examples and ideas for this type of magical clothing can be found here.