In Dead Rising 2: Off The Record for the PC, PS3, and Xbox 360, the Ninja Costume can make you quite a bit more stealthy. While wearing any part of the costume, you will be less detectable by regular zombies.
The Ninja Footwear can be found in The Man’s Sport store in the Uranus Zone, on a rack on the left side of the store.
Check out my other guide if you’re looking for the rest of the pieces to the Ninja Costume.