You can query DB directly -
This of course requires you don't prune log files. Alter LIMIT to whathever suits you, example above returns TOP 100 returning bouncers.
cheers
SELECT idvisitor, inet_ntoa(conv(hex(location_ip), 16, 10)), count(1) FROM piwik_log_visit WHERE visitor_returning = 1 AND visit_total_actions = 1 GROUP BY idvisitor ORDER BY count(1) DESC LIMIT 100
This of course requires you don't prune log files. Alter LIMIT to whathever suits you, example above returns TOP 100 returning bouncers.
cheers