Try Red Hill Sheaths…I don’t have any experience with them, but they seem to have a good reputation.
http://www.redhillsheaths.com/index.html
Also, SKD sells the Spec-Ops sheaths. They come in two sizes and are a universal fit depending on blade dimensions.
http://www.skdtac.com/SearchResults.asp?Search=knives&x=0&y=0
Glad to help.
This what I went with.