Blade Rigs makes some of the most purpose driven knife sheaths available. They excel at developing sheaths for small, self-defense oriented knives and often offer packages that bundle a knife with one of their sheaths. Their latest such package includes the Boker Newton Martin K-Bit and one of their pocket sheaths.
The Newton Martin K-Bit is a compact karambit design that will pretty much disappear in your pocket. The sheath is designed to be compact enough to compliment the K-Bit. It features a large thumb tab that can be used to push the sheath off with your thumb or caught on your pocket during the draw.