I have a bolt in mine. Works ok, I think would be better with a drill press. Making your own would be good too. You can get a mandrell for an electric motor at the hardware store.
He has the head listed separately now.
http://cgi.ebay.com/Fantastic-Leather-Burnisher-HEAD-ONLY-NEW-Even-Better-/220721077173?pt=LH_DefaultDomain_0&hash=item3364005bb5