I would go to a rescue. There are lots of them that post on here. If not, get one from the free ads in the paper, but make sure it is one that is rehoming their pigs for a genuine reason. Dont buy from the breeders, or people who have let their pigs breed to make some cash. Rescuing is much nicer. You love them a ton more and feel you have done a good deed. Its very rewarding.
I wouldnt even think about going to a pet shop anymore, as everytime somebody I know gets an animal from a shop it turns out to be ill, or the wrong sex.
Good luck finding your perfect pigs!