We say we're going to do it, but then we never get around to it. Now someone else has assembled, all in one plastic box, first-aid supplies for your dog, cat, bird or hamster. The Pet Care Kit is an emergency first-aid and home-care package that contains basic dressings, medications and medical instruments such as a thermometer, tweezers, scissors and surgical gloves. A manual, written by a veterinarian, not only has simple directions to follow for mishaps that may occur at home or during travel but also alerts you to the symptoms that demand a veterinarian's attention. Subjects covered include how to bandage an animal, and what to do if your dog or cat is stung by a bee or bitten by a snake, poisoned, choking, suffering from heat stroke, having convulsions or hit by a car. The kit comes in two sizes: small for cats and small dogs and regular for medium-size and large dogs. Each is $28 (includes tax and shipping) from Petcetera, 10949 Irma Ave., Tujunga 91042.