Need some rechargeable batteries

Our christmas gift for Alex was a robosapien.He really like it coz it can talk,dance,walk,take,throw some objects and some other functions.Eversince he got it,he never stopped playing until the batteries cease.For us,it's kind'a expensive coz the robot needs 10 or more (big and smaller)batteries and the ones we bought did not last long.That's why next time,we will buy some good rechargeable batteries so that we can save some money.I told Alex,he can turn on his robot all the time after we buy the rechargeable batteries.