I've never kept them alive in the store tub very long, I usally move them to something where they have more space. You can use almost anything as a container (small kritter keeper, Tupperware - just make sure it's ventilated.) give them some greens or cucumber to eat along with enough bran and/or oatmeal for bedding that they can burrow away.
I order them online and they can last for months if kept well.