Hi Dave,
I buy USDA Choice whole, untrimmed briskets in Cryovac at Dittmer's Gourmet Meats & Wursthaus at 400 San Antonio Rd. in Mountain View (650-941-3800). They use a lot of brisket to make their own pastrami, but call in advance to make sure they have them in stock. Ask for Mark and tell him you want a whole brisket for "Texas BBQ", as he calls it. They usually have 11-12 pounders.
I also understand that Lunardi's supermarket carried whole briskets in the past. The closest location to you is at 720 Blossom Hill Road in Los Gatos (408-358-1731).
Don't expect reasonable prices around here because whole briskets are hard to come by. Expect to pay about $2.69/lb at Dittmer's. You can pay about half that price if you buy by the case from places like Durham Meat Co. in San Jose. But you've got to be able to store and use 120 pounds of brisket.
By the way, keep your eyes peeled at Costco. The one in Mountain View had large brisket flats last year around Christmas.
Regards,
Chris