Like GuilloteTesla already mentioned, check the devwiki page.
I think original PS3 HDD are always Fujitsu, Hitachi, Seagate or Toshiba brand.
2.5" form factor, 20, 40, 60, 80, 120, 160 ,250, 320 or 500GB in size and SATA-150 or SATA-300 interface.
If you can't find the drive this way you could...