Ok. That's my solution:
1. Create dir at /src/addons/Quotes/
2. put there file touch /src/addons/Quotes/Quotes_Index.php
<?php
namespace Quotes;
class Quotes_Index
{
your code here
}
3. In template insert
<xf:callback class="\Quotes\Quotes_Index" method="getHtml"></xf:callback>
It works well.