To put my two cents into this chat, I worked with the originals from the movie and had access to the London celebration kits. The material is a light black nylon with a black eyelet on the corner to keep it from blowing away too much. It looks like its canvas but that's all done through weathering. They did a LOT of airbrush work for the weathered look.
However, if you want a canvas look I do have canvas in stock and can make a canvas form of the kama. It would be a dark dark brown.
Hope this helps you guys in your debate.
-Tony