Bladerigs created a very slick Leatherman Wave sheath for a friend and it turned out so well that they are offering it for sale. The sheath is unique in that it can hold the multitool whether it is open or closed! It can even secure the tool via a soft loop with snap in either position. That is slick and very, very handy.
The sheath includes a large Tek-Lok to attach it to your belt/gear. Check out the Leatherman Wave OWB Pouch at Bladerigs.