Drupal Language Switcher menu item
I have a small module hosted on GitHub that does just that:
Locale Menu
From the README file:

Overview
Alters the href of any menu item whose title is &quot;English&quot; or &quot;Español&quot; to point to the translated version of the current menu item. If no translation exists for the current menu item, the link will point to the translated version of the homepage.

You'll need to tweak Lines 6, 15, and (especially) 21 of the localemenu.module file to match the name and language code of your language.