What size do you want? That 500gb I posted is the best you're going to find for the size but if I know exactly what you're looking for, I might be able to give you what you need.
The seagate drives are cheaper and IMO and many others, way better then western digital. look for a 2.5" internal 5400 rpm SATA. they run from around 49.99 to 99.99 depending on the size. Momentus drives recomended.