CowboyStudio 77mm Lens Cap for Canon Lens Replaces E-77U - Includes Lens Cap Holder
The lens cap Fits any lens with a 77 mm filter thread; manual or auto focus, digital or film. The attachable lanyard makes it easy to keep track of your lens cap. Simply attache this piece to your lens cap.  Then it easily slides onto your wrist when not in use  You can also attach it to your lens so it can still be attached to your camera when not in use.