How would you make about 400 bucks quick? I'm looking to buy a laptop.?

Okay, so I've got a laptop in mind (and I'm not changing my mind about it). I've already blown off my recent $100 from a bunch of summer work on a Quake 3 server (paid out for a year). The laptop i'm looking at is $420, cheap & simple, and I can get some 10 or 20 bucks from chores/yardwork/etc. But I want to find out how I can make ~$400 in a fairly short amount of time. I'm 15 and it's school so I can't really get even a part-time job... So, if you were 15 and looking for a laptop that's on low supply and price (it's an open box deal, only limited number left) how would you make ~$400 quick?