This is one of the slickest approaches to a MOLLE compatible Kydex sheath that I have ever seen. Kinetics Concepts Tactical created this sheath for the Wenger Blades SPIKE. It attaches to PALS webbing without the need for hardware and sits nearly flush with surface it is mounted on.
The design is very, very clever and looks like it could be adapted easily to other slim knife designs. Check out Kinetic Concepts Tactical.