Most pet stores will sell live male mice as pets. Around here you have to either go to Petco or buy them from a reptile store as feeders if you want a female. Petsmart won't sell both sexes because they want to discourage breeding them.
what about petland? theres where I got all four of mine 2 boys 2 girl and I told them thats what I wanted. petsmart should sell you what ever you want. tell them you want that sex cause you have the oppisite sex and dont want them knocked up. lol. my petsmart dont sell feeders besides crickets.