I ran across this a while ago but I'd forgotten to post it. It's a generic USB driver for Windows 98 that should work with any device that supports the USB Mass Storage protocols... so it should work with any USB flash device, portable hard drive, etc... even if the manufacturer doesn't make a driver for Win98 available.
Installing USB Mass Storage Devices on Windows 98
I know someone was having trouble with Kingston refusing to support Windows 98... so this should help.