Please check your local rules to confirm allowable voltage, battery chemistry and ampere-hour as these differ by region. This article is NOT a substitute for the rules.
Batteries (nor Charger) are not included in the Freescale Cup kit due to global shipping complexities. Batteries can be hazardous if not stored, used and/or disposed of properly.
This format battery is fairly common in the radio controlled toy industry. Start your search at any local electronics store where Radio controlled toy's are sold.