...since Windows 98SE has been unsupported for so long, I doubt if you could find any new ones with drivers on them. You might look on Amazon or ebay, but I'd look for drives very low capacities relative to the ones that're out there today. I believe XP was the first version of Windows that would automatically search for and find drivers for these.
I have a printer connected to this PC plus a monitor and keyboard and can see a couple of unused ports I'm assuming are USB ports. (Also, this machne is not connecred to the internet.)