MacOS – Make Link shortcut

You don't need to map the power button, that menu is already mapped to control+eject

Other useful shutdown/restart/logoff key mappings are below which might be of interest too

Prompt to save work and restart the Mac - Control+Command+Eject

Prompt to save work and shutdown the Mac - Control+Option+Command+Eject

Sleep - Command+Option+Eject

Sleep displays - Shift+Control+Eject

If the computer isn't responding and you need to force it to power off, you can hold down the power button for 6 seconds, you'll lose unsaved work though.

These power shortcuts are listed on the apple support pages

You could use a private.xml like this with KeyRemap4MacBook:

<?xml version="1.0"?>
<root>
  <item>
    <name>test</name>
    <identifier>test</identifier>
    <autogen>__SimultaneousKeyPresses__
    KeyCode::CURSOR_UP,
    MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_COMMAND | ModifierFlag::NONE,
    KeyCode::CURSOR_LEFT,
    MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_COMMAND | ModifierFlag::NONE,
    KeyCode::F19</autogen>
  </item>
</root>

Then use F19 as the shortcut.