Buy a hard drive enclosure. I think I'd first put the new drive in the enclosure and create the clone, then test to make sure the clone boots. After that switch the two drives. When you're done you'll have a bigger drive in your MacBook, plus a little external drive for extra storage.
Of course, backup important files first and don't just rely on the clone—I had a tested, backup clone fail immediately after a clean install! Fortunately, being a crazy person, I had a second clone. :D