Menstrual Cups

Where can I buy a menstrual cup and what's the best kind? I don't want to order one online because my period starts tomorrow and I just want one right now. I'm planning on going to the store tomorrow to get one but I don't know where to go. I am also getting one because I am going to my boyfriend's house and his dogs like to dig the tampons out of the trash and chew on them too which is so embarrassing. So what stores sell them and what is the best kind y'all think I should get?