Aside from "please stop making a new thread for every game you're requesting", it sounds like you should check out Goozex for older DS games.
It's the best way to get non-new-releases at a good price, assuming you have games you're willing to trade out from any system.
FYI: N+ was $11.99 at Amazon during the entire BF weekend, so you might be able to score a used copy of it more easily in the next month or so.
BONUS EDIT: Space Invaders Extreme just dropped to $9.99 NEW at Gamestop today.
while I was there, I noticed they had 3 copies of N+ used for $17.99 each.
I went with Legend of Kage 2 myself (also $9.99)