You're trying to get too much out of an old scanner. There are SCSI-ethernet bridges, but they're very expensive. It isn't a simple thing - you pretty much need a server in between.
You could share the scanner from the PC that's hooked up to it, but that's also problematic and would be very slow.
You really should consider getting a newer scanner - perhaps a networked all-in-one printer-copier-scanner. You can get a cheap consumer-level inkjet one like the photosmart Plus for well under $200, or get a more robust laser model that can act as a full departmental copier and laser printer as well, for more of course.