Just made a trip out to Central Milling, which is actaully called "Keith Giusto Bakery Supply". They have moved into a new location. 755 Southpoint Blvd, Petaluma, CA. 866-979-2253
They have a very large selection of organic bulk flours. Now, you can call ahead, and they will pack 5lb bags. They ask that you please call ahead though, otherwise, you will wait for some time. If you are buying in 25 or 50lb bags, no problem.
Under construction, is a Bakery School, on site, that will be open soon.
Please email me your contact, if you are intersted in bulk flour. We were told that if enough of us order, they will deliver to SF, as they deliver to the Ferry Bldg twice a week.