You can always check any local bookseller for it -- Barnes, Waldenbooks, Borders, etc.....I know it's a bit pricey (aren't they all?), but it'll be well worth it if it helps pull you through!!
If you have a Borders, Borders Express, or Waldenbooks by you, they have this great club you can join for FREE (in store):
You can ask them in the store when you sign up if they have this month's coupon (20% discount) and then they send them via e-mail frequently....really a BIG help for us struggling students!!
Also, check your school's library or local library...lol...I know, like you've got all sorts of time to do all this chasing around!!