You may want to check out, https://winworldpc.com/product/windows-98/98-second-edition. The website is also a reliable source and contains Windows 98/98SE ISOs that are bootable (OEM versions), so you would not need a bootable diskette (if the BIOS supports it).
Alternatively you can make your own bootdisk,all you need is to format a: /S a floppy and copy over the drivers from the website of whatever CD rom your system has and run them so you can run the setup from the cd.
You may want to check out, https://winworldpc.com/product/windows-98/98-second-edition. The website is also a reliable source and contains Windows 98/98SE ISOs that are bootable (OEM versions), so you would not need a bootable diskette (if the BIOS supports it).