If you don't manage to get your hands on the Wonderful World Edition DS package or, just don't want to fork out for another DS Lite, here's another option for you. Available from July 27th, Hori will be releasing a "Subarashiki Kono Sekai Accessory Set" containing a protector casing for your DS and an extendable original stylus for a price of 1449 Yen (US$12).
Only a week before the game is out!
While we're talking about Hori's great range of gaming accessories, let me take the opportunity to remind people there are fake Hori branded DS screen protectors floating about on the internet, particularly auction sites. Check out Hori's notice page for photos of the counterfeit products marked "A" and "B".