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")}