That laptop had two option the standard built-in and the ATI. The ATI was a 512 plug-in card you may find in a 3rd party supplier used. Try a google search.
No, it's not a plug-in card - the video chip is part of the mainboard. It's not removeable. Whether Intel or ATI, the video chip is not a separate card on this model as you can plainly see from the service manual:
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