When ordering from IBM it is the FRU (Field Replacement Number) that is important, as part numbers are subject to change.
Getting the FRU is easy - use
lscfg
# lscfg -vl hdisk0
hdisk0 U0.1-P1/Z1-A8 16 Bit LVD SCSI Disk Drive (36400 MB)
Manufacturer................IBM
Machine Type and Model......ST336607LC
FRU Number..................00P3068
ROS Level and ID............43353048
Serial Number...............000780F7
EC Level....................H12094
Part Number.................00P2676
Device Specific.(Z0)........000003129F00013E
Device Specific.(Z1)........1217C511
Device Specific.(Z2)........0002
Device Specific.(Z3)........03326
Device Specific.(Z4)........0001
Device Specific.(Z5)........22
Device Specific.(Z6)........H12094