Is there a CheckBox control with adjustable mark size? [duplicate]

I'm developing a C# WPF application, where some screens are to be shown on a separate touch screen, and the regular WPF CheckBox's mark (the square where you need to click) is quite small.

I've been looking for a solution, but I don't understand the MSDN reference from this other question, therefore I'm asking for another solution).

Until now, I've managed to get the height in order (by setting VerticalContentAlignment to "Stretch"), but now the mark isn't a square anymore, and HorizontalContentAlignment does not seem to solve this).

Without vertical stretching: (Ok, it's square but NOK, it's too small)

<CheckBox Grid.Row="1" Grid.Column="0" 
          Content="Geladen?" 
          HorizontalContentAlignment="Stretch"
          VerticalContentAlignment="Center">

Screenshot:

With vertical stretching:(Ok, it's large enough but NOK, it's not a square)

<CheckBox Grid.Row="1" Grid.Column="0" 
          Content="Geladen?"
          HorizontalContentAlignment="Stretch"
          VerticalContentAlignment="Stretch">

Screenshot:

Thanks in advance