There are some other sites like Autodesk's FTP. Don't use them because the drivers there might be outdated.
Be sure to read the Supported Cards List to ensure your new card is among the supported models.
Sometimes a driver for another card with the same chip could work.
If you can't find a compatible driver, use the "VESA Compatibles" driver. Note that you can use only 256 colors in all resolutions.