[calorie]

Untested but you could try adding the following code to the parse_templates hook:

vB_Template::preRegister('header',array('quickchooserbits' => $quickchooserbits));

And then use the following in the vBulletin header template wherever you want it:

<form action="{vb:raw vboptions.forumhome}.php" method="get" id="style_select" class="footer_select">
	<vb:if condition="$show['quickchooser']">
		<select name="styleid" onchange="switch_id(this, 'style')">
			<optgroup label="{vb:rawphrase quick_style_chooser}">
				{vb:raw quickchooserbits}
			</optgroup>
		</select>
	</vb:if>
</form>