Iomega stuff tends to be designed especially for their devices (Zip and Jaz drives), and I wouldn't recommend trying to make it work with anything else. As for SCSI-IDE and SCSI-SATA bridges, the ACARD ones work extremely well but are a bit pricey (the one I'm eyeing for my 475 is $140).
Why bother? Well, pretty much any SCSI drive old enough to work with a 475 without adapters has bad or noisy bearings, and a new 15k monster would be massive overkill for such an old machine.
(
ETA: Then again, if you can get a surplus 15k for free, it certainly changes things.
I managed to dig up a 2002-vintage Seagate 18GB that works fine and is deadly silent while running.)
-lee