Open up index.template.php and search for
if ($context['current_action'] == 'search2')
$current_action = 'search';
After that add this after
if ($context['current_action'] == 'shop')
$current_action = 'shop';
Now search for
// Show the [help] button.
echo '<li><a' , $current_action=='help' ? ' class="current"' : '' , ' href="', $scripturl, '?action=help"><span>' , $txt[119] , '</span></a></li>';
Now add this after
// Show the [shop] button.
echo '<li><a' , $current_action=='shop' ? ' class="current"' : '' , ' href="', $scripturl, '?action=shop"><span>Shop</span></a></li>';