Just got myself 8 AAs (Rechargeable) from IKEA for my custom 9,6 V battery pack which I use for my Nikko Super Cruiser. A bit overkill when you count the capacity lol. :
Replacement 6V battery for Nikko Tyco Taiyo RadioShack and more - Tyco Collectors
Replacement 6V battery for Nikko Tyco Taiyo RadioShack and more - Tyco Collectors
NIKKO 6.0V 650mAh Ni-Cd SLOT IN BATTERY PACK AND 4 HOUR CHARGER | eBay