Unable to setup Command + Shift shortcut on Mavericks
You can use KeyRemap4MacBook to for example map option-shift to option-F19 and control-shift to control-F19:

&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
    &lt;name&gt;test&lt;/name&gt;
    &lt;identifier&gt;test&lt;/identifier&gt;
    &lt;autogen&gt;__KeyOverlaidModifier__ KeyCode::SHIFT_L, ModifierFlag::OPTION_L | ModifierFlag::SHIFT_L | ModifierFlag::NONE, KeyCode::SHIFT_L, ModifierFlag::OPTION_L, KeyCode::F19, ModifierFlag::OPTION_L&lt;/autogen&gt;
    &lt;autogen&gt;__KeyOverlaidModifier__ KeyCode::SHIFT_R, ModifierFlag::OPTION_R | ModifierFlag::SHIFT_R | ModifierFlag::NONE, KeyCode::SHIFT_R, ModifierFlag::OPTION_R, KeyCode::F19, ModifierFlag::OPTION_L&lt;/autogen&gt;
    &lt;autogen&gt;__KeyOverlaidModifier__ KeyCode::SHIFT_L, ModifierFlag::CONTROL_L | ModifierFlag::SHIFT_L | ModifierFlag::NONE, KeyCode::SHIFT_L, ModifierFlag::CONTROL_L, KeyCode::F19, ModifierFlag::CONTROL_L&lt;/autogen&gt;
    &lt;autogen&gt;__KeyOverlaidModifier__ KeyCode::SHIFT_R, ModifierFlag::CONTROL_R | ModifierFlag::SHIFT_R | ModifierFlag::NONE, KeyCode::SHIFT_R, ModifierFlag::CONTROL_R, KeyCode::F19, ModifierFlag::CONTROL_L&lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;


Then change the shortcuts for switching input sources to option-F19 and control-F19.