We got some green cobra guppies last year at petco. I think that they had some yellow ones there too. I will never go there again though, as before they managed to get us our fish, the mentally uncapable (I am not trying to say this to be rude, it's just that this person could have easily been put in another department that does not involve netting live fish, really I am not biased I even have family that has a mental handicap that I love very much) employee had managed to drop a fish 5 feet onto the floor, and keep several others out of the water for way too long! They also do not take good care of their fish. I don't know if you are looking for show quality or not, but lots of people advertise extra guppies on craigslist as well. There are even people here trying to find homes for extra guppies. | 