Where can I buy a baby cactus?

i live in the midwest(sweltering hot in the summer, frigid cold in the winter) and fall is just beginning. i went to lowes today and asked the worker if they had any and she said they only get them in the spring. would any other store sell baby cactuses? i want one really bad! would it be able to survive in the harsh midwest winters? the windows of my house are really old so cold air seeps in so it can get kinda cold in my house during the winter.