Anyone know? Or have any ideas about where I can look? I checked the census figures, but the highest income bracket they listed was “200,000 or more.”
Let me tell you being a millionaire is no big deal. I imagine there are too many in San Francisco to count. Remember Bucky Hunt said “If you know how much you’re worth, you’re not worth very much.” 
And income is not really an indicator of being a millionaire. You could own a million dollar penthouse and work a part-time job for $25,000 a year. Or you could earn $5,000,000 a year and blow it all on crack and hookers.
No one has ever stated my dreams so clearly before …
Wealth data tends to rely on thinner samples than income data. I’m guessing that the SIPP or the Fed’s Survey of Consumer Finances won’t help you much.
I don’t remember whether the census asks wealth questions: my guess is that it doesn’t.
If you do find a useful wealth indicator in the census long form, you could try using PUMS directly. Be sure to get at least a rough indication of what sampling errors you are working with.
In the end, I suspect that you may have to reframe your underlying question.
Best wishes,
M4M