http://www.amainhobbies.com/product_...oducts_id/7116
I dont know where to get one in the UK as I am in the USA but this is the one I am talking about using in the V-Spec. Unfortunately when I sold the V-Spec I forgot to remove it.
The one I use in my Ninja is the 7mm one that comes with the Speed engine. Its a red aluminum one. The new version of the JX Ninja the BO1A comes with the same 7mm aluminum one but its the gray Mugen color instead of red.