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
You can get ideas in these threads.
http://leatherworker.net/forum/index.php?showtopic=21201&st=0&p=136530&hl=workbench&fromsearch=1entry136530
http://leatherworker.net/forum/index.php?showtopic=1321&st=0&p=32042&hl=workbench&fromsearch=1entry32042
http://leatherworker.net/forum/index.php?showtopic=826&st=0&p=28147&hl=workbench&fromsearch=1entry28147
http://leatherworker.net/forum/index.php?showtopic=14826&st=0&p=92008&hl=workbenches&fromsearch=1entry92008