What snake will live happily in a kritter keeper?

None ! Critter keepers are not designed to be permanent homes for reptiles. The plastic construction is unsuitable for heating to the (often much higher) temperatures that many reptiles need. Snakes should be housed in a wooden vivarium, with the correct lighting, heating and (if necessary) humidity in order to allow it to live as naturally as possible. Snakes need space to move around. Even a garter snake will outgrow a critter-keeper in a very short space of time !