Really? I thought the internals were different, because someone over on the IIGS Facebook page said that you can fry the RFI input. I actually have S-Video cables lying around, but the new cable comes Monday anyway.
I have no idea what that FB person means by RFI input. There are only two real differences between an apple keyboard cable and an s-video cable.
The apple is coiled and most S-video cables will have better shielding due to that part that they are for analog video.
But if you get bored of dealing with ADB keyboards / mice and want to use modern USB hardware - Big mess o wires make an ADB to USB adapter called the "Wombat" for about $50.
Works with any apple product that use ADB (like 90's macs and IIGS), It also two- way. Meaning you can also use an Apple ADB keyboard with just about any computer with an USB port.