Universal sheath for all Mk. 4 and Mk. 5 Shiny Knives.  Any model of Shiny Knife with a mid-ring is retained by a pincer on the sheath. The pincer clips in to the ring, which will require some force to remove.  If this action feels too stiff, you can wear it in, sand it down, or uninstall it.  Without the pincer or mid-ring, the sheath will still grab the knife, but it could shake loose when wallrunning, backflipping, etc.
 
Use the pivoting belt clip to attach to a material edge up to ~1/4" thick.  The sheath can also be tied to something using three mounting holes.  The belt clip can be reversed to the other side, or removed.  This updated belt clip's rotation is held firmly in place by friction, but is still easily rotated by hand.
 
The sheath in the video is an older model with no ring pincer.