Hello Rob, nice to see you also here ;)
The widgets of Mendix can be found on Github: https://github.com/mendix/widgets-resources
But some widgets are a bit special. To my knowledge the datagrid widget ( https://github.com/mendix/DataWidgets-module ) is the only one because some of the functionality is tied to the Mendix modeler version. So only by upgrading your model could you upgrade your datgrid widget.