Hi Kathy,
Is it possible that the reference you have to Fond Du Lac is not in Wisconsin, but the Fond du Lac reservation in Minnesota. Just a shot in the dark. I know that when I first started genealogy, I only knew of the Fond du Lac in Wisconsin also, until I found an old atlas that had the reserve on it.
Let me know if this helps.
email at the above address and let me know.