From the state that popularized purse puppies, drive-through dog washes and gourmet dog food delivery comes the latest in canine convenience out of California: a company that contracts out dogs by the day to urbanites without the time or space to care for a pet full-time. FlexPetz is currently available in Los Angeles and San Diego and will open in San Francisco next month, New York in September and London by the end of the year. For an annual fee of $99.95, a monthly payment of $49.95 and a per-visit charge of $39.95 a day, animal lovers who enroll in FlexPetz get to spend time with a four-legged companion. The membership costs cover the expense of training the dogs, boarding them, home or office delivery, collar-sized global positioning devices, veterinary bills and liability insurance. It also pays for the leashes, bowls, beds and pre-measured food that accompany each dog.