The Fletcher Hanks Redux project that was linked to from a previous post had a pretty good Fantomah story that provided an origin, partially addressed the "white woman's burden" issue (Fantomah is an Egyptian woman whose hair has been bleached white, not a Caucasian blonde), and if I remember correctly put her in an urban setting (which might still be in Africa). I think it would be a perfectly workable premise, and could retain a lot of the specific character of the original.
The site seems to be down right now, but since that also goes for the whole college website, I'm guessing it's just a temporary outage.