People use the "spare" steel wheels on FJ's... I should think they will fit your 100 series too. Or if you have a steel spare that's different than the FJ spare wheel, there you go. Order 4 more from Toyota. ??
Great idea unfortunately my spare was a full sized spare with the original Toyota 18" alloy wheel. My local Toyota dealer who I asked this very question "Do you have steel spares that will fit my truck" could only offer officially sanctioned alloys of various sizes starting at 16" for ~$550 per wheel. Online, you can find these same OEM part numbers for ~$300ish...which isn't really going to work for me.
So now I've got my beloved BFG AT KOs on wheels that I don't love but will be fine just in time to go get dirty and camp in Nevada with my family.