Source for duck and goose liver in San Francisco area
If you're looking for Foie Gras it would seem that Sonoma Foie Gras would be the spot but the web page gives no contact information:
Polarica has always listed both liver and foie gras for sale. No idea if they stock it or what quality or freshness they offer.
Liberty Duck in Sonoma County would be another source to check with:
Checking with the companies should get you answers about what's available and where.