"It's been a tough night. Some idiot's started selling Metamorph-Medals. Just sling them around your neck and you'll be able to change your appearance at will. A hundred thousand disguises, all for ten Galleons!"
-- Arthur Weasley (HBP5)
If you believe the advertising, one of these will give the wearer some of the abilities of a Metamorphmagus for only ten Galleons. In fact, the changes in the wearer’s appearance aren’t under his or her control, and not only make the victim more rather than less conspicuous but can require hospitalization to undo (HBP5).
When the wizarding world was on edge about the return of Lord Voldemort in 1996, some people bought into the scam of Metamorph-Medals, thinking that they would help hide and protect them.