This template was released on October 14, 2007, from this
Topic in which I requested a button until I finally figured it out by myself.
I'll just post here on what I have so far
Find
if ($context['current_action'] == 'theme')
$current_action = isset($_REQUEST['sa']) && $_REQUEST['sa'] == 'pick' ? 'profile' : 'admin';
After this code, paste this
if ($context['current_action'] == 'shop')
$current_action = 'shop';
Now Find
// The [calendar]!
if ($context['allow_calendar'])
echo '
<li', $current_action == 'calendar' ? ' id="active"' : '', '><a href="', $scripturl, '?action=calendar">', $txt['calendar24'], '</a></li>';
And add this after this code
// The shop
echo '
<li', $current_action == 'shop' ? ' id="active"' : '', '><a href="', $scripturl, '?action=shop">Shop</a></li>';
And you're done.