HDDs for Netfinity 5500

[afactor]

Does anybody know a good place to get discontinued hard drives.
Specifically I need to get some hard drives for an IBM Netfinity 550 midrange server.
IBM has discontinued virtually all the parts for this old workhorse and they pointed me to their affiliate called Boulder Parts.
Boulder parts gave me the following prices (and told me they are about out of these parts):
4Gb - $450
9Gb - $600
18Gb - $1000

Can anyone suggest an alternative?

Thanks,
Alan
afactor at afactor.com