From memory it's a Fujitsu or Toshiba drive, with a 9.5mm height (currently residing in my Nomad Jukebox 3 ;-))

Upgrading the NJB3 was pretty easy, as long as you are licensed to wield a screwdriver. I've not seen a Karma opened, but might take the risk (as chances are I will have no warranty where I am buying it from anyway).