Before you choose to put a vest on your pet, please think about how hard people have fought to get rights to service animals. Just one situation gone wrong gives people the means to try and take away the rights from others who really need them. (I apologize for the poor quality. I took the picture as I was walking into the establishment).
Comfort, Emotional, Therapy, and Companion dogs are not always permitted where Service Dogs are allowed. You can learn more about Service Animals at https://www.ada.gov/service_animals_2010.htm