Pegasus in Danville.
I was very surprised so few places rented bikes when I needed one for a visiting friend last March. Pegasus was the only one I could find in the East Bay which turned out good as we wanted to climb Mt. Diablo. My friend ended up with a Scott with all Ultegra 10 speed components for $50-$60 a day. They even put the saddle he was used to (Fizik Aliante) and the pedals that fit his cleats (Speedplay).
Their service is impeccable.
Oops! I just notice you were looking in the Peninsula.