I got two different converters as i went into buy two from maplins and they only had one left so got that one and another from D&G hardware in winch.
On the boxes it says "100 watt international electricity converter" dunno who its made by as doesnt say on the box and the other "45 watt Plug in voltage converter, UK (230 Volts AC) to USA (110 Volts AC)" made by SUNPOWER. As long as the wattage is over the wattage of the decks their fine, think its 12W.
But basically any decent electrical / hardware store will sell them, if your not sure bring one of the decks in with you and show them what you got they'll know what you need. Dont go to big places like Homebase or B&Q as i couldnt find anything in either.