Upgraded to windows 8- no driver for graphic card

Hi all,
I just upgraded my laptop to windows 8.1 Pro x64. I have a Sony Vaio laptop,VPCEA1S1E, with an intel core i3 cpu and 4 GB of Ram. My main problem is that i can't find the latest driver for my graphic card which is the ATI mobility Radeon HD 4500 Series. When i open my device manager, i find two alerts under unknown devices. How can i fix this?
