I found a legit sword pencil before level 7 on my 3rd run through of the game. (I was deleting saves to get the special drawings). It works as if I really got the sword pencil on level seven. Read on to find out more.
Here's where I found it: after I jumped off the easel, instead of heading towards my friend and the book, I went left. I met an invisible wall, but I was able to find a "hole" in it. On the other side of this wall was a sword pencil. I picked it up, but nothing happened. I had to walk through the exact same spot as I walked in to get back to where I was supposed to be. When level one started, I had access to the sword.
Weird, eh? Dunno if it's a secret or whatnot, but it really helped me on this playthrough.