[kh99]

Looking in functions_forumlist.php, it looks like the parameters to fetch_forum_lightbulb should be forumid, lastpostinfo, foruminfo. Stealing some code from that file, you might be able to do something like this (assuming $forumid is already set):

global $vbulletin, $lastpostarray;

// call fetch_last_post_array() first to get last post info for forums
if (!is_array($lastpostarray))
{
	fetch_last_post_array(-1);
}

// grab the appropriate forum from the $vbulletin->forumcache
$forum = $vbulletin->forumcache["$forumid"];

$lastpostinfo = (empty($lastpostarray[$forumid]) ? array() : $vbulletin->forumcache["$lastpostarray[$forumid]"]);

$sioc = fetch_forum_lightbulb($forumid, $lastpostinfo, $forum);

And then if you look in functions_forumlist after fetch_forum_lightbulb is called you can see there's some additional code to add the lock for locked threads, if you care about that.

I didin't try any of this so I'm not sure if there might be something else you need to do.