These were made by Comarco (brand Chargesource), they definitely have tips.
http://www.chargesource.com/store.php (check
http://www.comarco.com/news/33 a 2010 PR for an official source they made these: "we continue to ship our ‘Ultra Slim and Light’ product to Lenovo" but now
http://biz.yahoo.com/e/150430/cmro10-k.html they are essentially over that Lenovo no longer sells these. Better get a spare tip or two
)