Adding quick style chooser to a template

[riotous]

I found the code to add the quick style chooser but it looks like it's making a call to a JavaScript function that I can't seem to find.

	<form action="{vb:raw vboptions.forumhome}.php" method="get" id="footer_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>
		
		<vb:if condition="$show['languagechooser']">
			<select name="langid" onchange="switch_id(this, 'lang')">
				<optgroup label="{vb:rawphrase quick_language_chooser}">
					{vb:raw languagechooserbits}
				</optgroup>
			</select>
		</vb:if>
	</form>

So the switch_id() function. I did a template search in a template with a working quick style chooser and it only returned a result for the footer, which only has those two occurrences of switch_id. The quick style chooser displays but when selected, nothing happens - as if a script reference is missing.

P.S. - The style chooser is enabled and works on other themes. But this theme was written without one (stripped down mobile theme).

Thanks.