Hi

I am looking for a needle valve extention cable for a OS 46 AX .......any alternatives avaiable 

The whole needle extension assembly, the fuel line (cable?) or just the little L-key shaped part that you use to turn the needle ? Just clarifying

Going by what you say, Looks like you are looking for the braided cable which is supplied these days with most of the OS engines.
Do not bother much, use the clutch/brake cable from any two wheeler as long as it fits the needle and make sure you threadlock the grub screw. If you have lost the grub screw that should be also easily available from auto shops as OS uses metric sizes