where can I buy the OS X installation disc for my 2009 macbook pro 13-inch and the applications disc?

I lost my OS X installation disc and applications disc. I had to restart my computer and erase all my info off the hard drive because my computer wouldn't turn on all the why. Be sides that I need to buy new disc and i don't knot where to buy them. I tried are iMac disc it works but it can't be installed because its mac and not macbook pro. please help. i was on the phone all day with apple support yesterday and I'm getting so close. after i erased everything i had the option to install OS X mavericks but it keep saying try again when i wanted to install it. but then i put in the iMac OS X installation disc in it didn't give me that option any more when i took the disc out and powered the macbook pro back up a folder you a question mark pops up and it just starts flashing what do i do.