Why not just replace it
There's probably not enough room, from what I've seen of the inside, but it is pretty darned easy to rip the old one out and put in a new, bigger one (I'm not too computer saavy, but I did it in less that 30 minutes - all it too was the right sized Torx, and some gentle fiddling). If you're worried about getting the info off the old drive after you've removed it, just get an enclosure for it, and you can copy the data off it onto the new drive, and have an external drive for backups!