I think the only bad part about brains is, you have to cook it and it probably oxidizes big amounts of cholesterol.
I can save you one call.
I tried at Belcampo Meats in Larkspur, but they don't have them.
They said there was extra processing and certification requirements for their butchers to handle brain/spinal cord tissues, which they do not yet have.
There are many sources for organic grass fed animals in the north bay. Check Eat Wild dot com. Call around and see if anyone will sell you brains.
(Resisting the urge to make SO many jokes here!). Mmmmph ...