I buy my batteries and charger (imax b6) at hobbyking. Buy a 2Slipo (7.4 volts) the higher the mah, bigger the battery and longer you will drive. Im using 5.600 mah.

I recomend you to bin the tamiya connectors and use XT60 or Deans. Replacng the connectors is very easy, you just need the solder iron and some heat shrink tube. Look for the connector name on youtube and you will find tutorials.