React mui dialog body padding with custom scrollbar

I have a React mui theme with a custom scrollbar like this:

ui.material.createTheme({
  components: {
    MuiCssBaseline: {
      styleOverrides: {
        '::-webkit-scrollbar': {
          width: '100px'
        }
      }
    }
  }
});

Then I use a Dialog. This adds padding-right and overflow to the body:

At this point padding-right: 19px is incorrect. It should be 100px. What is the appropriate location to override these styles in mui? I'm aware I can add a CSS override for this situation but I'd like to solve in the proper, supported way, that mui probably provides somehow.