Replacing a 4 year old SCSI drive?

Spent all afternoon properly decomissioning an oldish server, then rebooted so I could begin to wipe it and start again, and Im told there is one drive out of the RAID5 array missing :evil:

Tried pulling it out and reseating it a few times but no good, I suspect it may just be faulty.

Im not sure what the capacity is off the top of my head but the manufacture date is December 2002 (strange considering the server was purchased in March 04...) and is a Fujitsu

Are we likely to be able to get hold of another one of these drives? Or would a larger, newer one be ok? (I realise I would only be able to use the equivelent of the capacity of the old drive)