id go for vapextech great value and products

either 2 7.2v
http://stores.ebay.co.uk/Vapextech-Batt ... 34.c0.m322

(the large the mah number the longer they will last, if you go for 2 of these get the same mah value)

or a single 12v

http://stores.ebay.co.uk/Vapextech-Batt ... 34.c0.m322