Please suggest battery for Devantech RD02 - 12 Volt Robot Drive System

Could someone suggest a battery and recharge solution
for this robotshop.com/ca/drive-system-12-volt.html ?

Preferably something I could buy from Robotshop.

It’s a 12V system, so something like RB-Hpr-06 would work well. You could use RB-Ten-02 to charge it and RB-Onl-12 to make it easy to connect it to the controller. We plan to release a higher capacity 12V pack (9.5Ah) in the coming weeks, though it will cost quite a bit more.