MUI: Modify appearance of back button

How can I easily override the styling of the back button. It's currently buried in ModernWindow.xaml, and I'd prefer not to compile in all of MUI into my solution.

<!-- back button -->
<controls:ModernButton Margin="8,10,0,0" HorizontalAlignment="Left" VerticalAlignment="Top"
                       EllipseDiameter="24" IconWidth="12" IconHeight="12"
                       IconData="F1 M 33,22L 33,26L 19.75,26L 27,33L 20.5,33L 11,24L 20.5,15L 27,15L 19.75,22L 33,22 Z"
                       Command="NavigationCommands.BrowseBack"
                       CommandTarget="{Binding ElementName=ContentFrame}" 
                       ToolTip="{x:Static modernui:Resources.Back}"
                       WindowChrome.IsHitTestVisibleInChrome="True" />

I just want to make it a little bigger and give it a background color of the current highlight color (i.e. blue).

I have a request to make it look more like the huge blue back button in Internet Explorer.