Hiding members list from visitors

I would like to hide members list from visitors, and show them a login screen like other parts of the forum which does not permission.However, I am not sure what else to add in to the "else" part to get the login screen exactly the same. It is missing the "important" message, how may I get that message?

Here is what I did:
<xen:if is="!{$visitor.user_id}">
<xen:else />
There is an add-on for this, but I can't find the link. :mad:
Thanks I have solve my problem by adding:

<xen:if is="{$visitor.user_id}">
"member list"
<xen:else />
    <xen:set var="$text">{xen:phrase login_required}</xen:set>

  <xen:include template="error_with_login" /> <-------------------------------