Yes, Gourmet Rodent supplies Petco with their corns and boas and also other assorted reptiles.
Whether you purchase from a pet shop, including Petco, really depends on the care and cleanliness that particular shop happens to have. I know some people say you should never do so at all and they have their views on it. But the way I see it, some are good, some or mediocere, and some are just plain attrocious. IF you find that the store you frequent takes proper care of their animals and keeps their housing clean, then I, myself see no problem with purchasing from them. IF you see that their cages are not kept clean, and that includes rodent housing and bird housing, then I wouldn't touch their pets. If one section of pet's housing is ill cared for, then you can surmise that, even if the housing of the snake looks ok at that visit, that they are not properly cared for and you could easily be buying a problem.
I happen to have a very well kept Petco near me that I have purchased a few corns from. In fact, my very first ones came from there. Accept for those 4 corns and 2 boas, all of my large crew of snakes come from breeders. I personally would stick basically to known breeders, but sometimes a certain snake will just take your fancy and you just "have" to buy it.
Here are my "Petco" purchases. The anery stripe was purchased this year (the only corn petstore purchase this year) because I fell in love with his looks and he came home with me.
Good luck with your new pet. I'm sure you are going to enjoy it.