There is no way to install a new graphics card onto the motherboard. I have heard of External graphics solutions, but none that are up for retail right now. I doubt your laptop has a thunderbolt input, so I don't think daisy chaining would be an option either.
I'll look a little bit more, but it seems you are out of luck.
Good article to read, but any external solutions require thunderbolt + an enclosure + a discrete graphics card. Even if you had thunderbolt, you are still looking at about a 800-1000 upgrade.