You can get (I have got) USB keyboards and USB mice and both can be cordless.
Just one thing to beware of with win 98 and older motherboards/bios is that USB is only supported by windows, not the MB. So if you want to do stuff in DOS or in the bios setup before windows has loaded usb bits won't work so keep your old keyboard as a standby - someone may correct me on this but thats how it works on my son's win98 machine.