Good sharpener for bourjois pencils?

i understand you cant sharpen these with normal sharpeners. i see that bourjois has a brush set which includes a sharpener but i really cant afford the whole set right now. is there another store that sells just the bourjois sharpener alone, or another brand that will work? these pencils are odd, please answer if you know for sure a sharpener that will work on them. thanks!