I found the solution to the problem:
1. USB Charger for Nokia - I bought the USB charger for mobile phones for US$3.60.
2. Power port - one side to the airplane.
3. Power converter to change the airplane power to USB.
Both 2 and 3 costs US$40.
I bought the #1 and still thinking whether it is a wise choice to just buy a few more spare batteries instead of that power converter.
Just found the comment on
http://www.lovemyseat.com/airlines/U...t_Service.html referring to United:
"B767-300s, B747-400s and B777s aircrafts have in-seat power availabe in First and Business classes; all classes have laptop power access on transcontinental flights; no power adaptors required."
Is it true????