How can i make 700- 1000 dollars, some what quickly?

I've been looking to buy an alienware laptop- but im 12- and my dad said if i can get half or so that i could put it down and he would pay the rest of monthly by taking the monthly fee out of my allowance. I need the money in about 5-6 months and none of the ideas I've had have worked, and I'm sorta lost. if someone could help that would be great, thanks