I'm no computer whizz, but i think the main reason you're probably having problems finding an internal drive for your laptop is that there is pretty much quite slim support for anything internal with regards to a laptop nowadays- once your portable friend packs in, then theres not a great deal you can do, apart from take it to a technician - upgrading them is almost out of the question i think.
That being said though, i'd keep looking - IBM sell individual drives for their laptops, so there must be some kind of support from your manufacturer.