You'll have to make it yourself! (Or, become famous and get fans who want to make them for you)
If you dig through the nin.com blog archive you can see photos of one of the dolls taken in Hong Kong, Sydney and Honolulu last year on the second leg of the Year Zero tour.
They (or at least the centre one all in black) were made by fan/s. So if you want your own, dig out those old Ken dolls - I know some of you still have them - and get cracking!
**Edit** Today Angulique let me know that these dolls were made with Dragon and Ultimate Soldier figures. Thanks!