You can get any ATA drive and it will work. They are not Mac or PC specific.
Don't worry about speed either. Your Yikes has a ATA/33 bus, but ATA/66 /100 or /133 will work just fine. They automatically slow down to the bus speed.
If you don't have a Zip drive, you can also put a drive in that bay. It's an even slower connection, but for another 10GBs of space for the heck of it, it works fine. I would put the newer and likely faster drive on the main bus and move the smallest/slowest one to the Zip bay.