need to create Drop down list of categories (menu) as Widget

hi , i need to create a drop down list in widget

i can put some code like this in my widget as code :

<select autofocus>
<option value=”volvo”>Volvo</option>
<option value=”saab”>Saab</option>
<option value=”opel”>Opel</option>
<option value=”audi”>Audi</option>
</select>

but it`s not dynamic and nice

i search for plugins but couldnt find any , and i found some tutorial on web like put these code in header.php

<?php
$arr = get_categories();
echo “<select name=’categorylist’>”;
foreach($arr as $option){
echo “<option value='{$option}’>{$option->name}</option>”;
}
echo “</select>”;
?>

but i dont want to edit template too !! so do you know any plugin for that ??