You might also look at Nylon sheaths.

Spec-Ops is a really good company and I have my YKLE in one of their survival sheaths.

The sheaths have a thermoplastic insert that can custom formed to the knife of your choice.

I guess these are kind of a cross with kydex and leather, minus the leather part and replace it with more plastic. <img src="/ubbthreads/images/graemlins/laugh.gif" alt="" />

Here is their pouch sheath with Cloaks RD7