How do I add a Super Clone button for a community or partner portal site?

The custom button can be created with the global variable $Site.Prefix. This will return the path of the current community.

/* Super Clone */
{!URLFOR($Site.Prefix + '/apex/dh_superclone__superclone', null, [rid=MyObject__c.Id, cfg="MyConfig")}

/* Super Clone Pro */
{!URLFOR($Site.Prefix + '/apex/lcrm_scp__scpclone', null, [rid=MyObject__c.Id, cfg="MyConfig")}