The keyboard ribbon cable is a part of the Upper Case, which we sell, but there are many different versions of the "white macbook". Please ID Your Mac to determine which one you have. From there you should just be able to navigate to the parts we sell for your computer and select the Upper Case (it is listed as a Case Component).
As a side note, depending on the severity of the tear and it's location, it can sometimes be fixed. In one of my earlier Macbook repairs (about ~4 years ago) I tore the keyboard cable at the plug. I gave it to the best electronics guy I knew and he was able to re-solder it.