Add javascript onClick code to Thematic functions.php

I’m trying to add via functions.php the following link to all pages in a Thematic child theme:

<a href="#" onClick="window.open('https://foo.com', 'null', 'width=490, height=405, menubar=no, toolbar=no, scrollbars=no, location=0, directories=0, resizable=yes, status=0');return false">Live Chat</a>

If I drop this code into the main content area of a page/post, it works fine. However, when I call it via functions.php, it fails.

Here’s the function:

// ADD LIVE-CHAT LINK

function livechat() {
$stylesheetdir = get_bloginfo('stylesheet_directory');
echo '<div id="live-chat"><a href="#" onClick="window.open('https://foo.com', 'null', 'width=490, height=405, menubar=no, toolbar=no, scrollbars=no, location=0, directories=0, resizable=yes, status=0');return false">Live Chat</a></div>';
}

add_filter( 'thematic_belowheader', 'livechat' );

Anybody know what I’m doing wrong? And, more importantly, can someone please tell me how to do it right?

Thanks in advance.