A talented young woman has been kind enough to make a miniature version of the map, and posted it on the interwebz. You can find it here: http://britta.com/hogwarts/Year6/prep/map/index.html
Her directions were to print the drawing on regular 8.5 x 11 parchment paper - but to my chagrin, my wallet could not afford to buy any. So I did the next best thing. I aged the paper myself.
After printing out the drawing, I rushed over to Staples to make a number of photocopies of the map. I then made some strong black coffee, set my oven to 200 degrees Fahrenheit and followed the instructions I found here: http://www.curbly.com/users/diy-maven/posts/863-how-to-antique-paper
And here were my results:
This was so much fun to do. And the finished product is really adorable - fits right into the palm of my hand. I think I'll give copies along with any more magic wands I make and give as gifts.
Note: if you do plan to age regular copy paper, then make sure to do both sides of the map to keep the color consistent since both sides are viewable after folding.