My local PetCo knows my husband and I as snake owners. One of our BP's won't eat anything unless it's live. We usually go to a small pet store to get our food - we're friends with the owner and love to support small businesses. One day he was out of rats in the size we needed so we went to PetCo. They sold us a live rat without hassle. This has happened a few times and we always get a live rat without any problems.
I think it varies by store.