CRK sources to Gfeller for their leather, high quality stuff. I have had a couple (still have one) and while it is a great design for a work belt or for outdoors, it is too bulky in design and construction for urban wear.
The leathersmiths indicated above (Vess and Lifter) are excellent, as is G2 leatherworks.
Having or presently owning sheaths from each, I can say without dear of contradiction that you can not go wrong with whichever you choose. The quality and workmanship will be excellent. Therefore, perhaps a quick look at their respective websites will determine which you find most pleasing to the eye.