Weapon Accessories?

For a grappling hook, I think you could try making a pinnhole in a 6 inch scale gun with a needle, and then put a bendy wire on the end of it (maybe use a small fishing hook for the hook itself).If that would look a bit modern for a feudal ninja for you, just lose the gun part. As for the shurikens, why not just cut them with an exacto knife out of a soft,thin layer of plastic and then paint them? They may not look perfect at a first try, but as you get better at customising, so will be your accessories. Just some ideas. Good luck!