That is the only photo I have seen of someone who made it. But here is how I would personally go about making it.
First of all, is it just for a photoshoot or for a convention? Because durability may be an issue.
For the actual staff part, just get a really long dowel rod or two short ones and wood glue them together. For the top part, I would use sculpy. The problem is that it may break.
You could also use model magic to mold the top parts. I used model magic to make the flower's on Kairi's keyblade, and I would never hit it against something because it WOULD break, but if you are careful and MAKE SURE you let it dry for 3-4 days before you paint it, it should work.