So it is a 2.5 inch drive which means any other 2.5 inch drive will fit.
I'd suggest a WD Blue 500 Gb. http://www.amazon.co.uk/500GB-inch-SATA-Internal-Drive/dp/B00C9TECFO/
You'd need to either clone your drive, which can be done by purchasing a SATA>USB adapter, or by fresh installing your OS - I heavily recommend the latter. We can guide you through whichever you choose.