These types of needles are easily soldered since there is ample hole left off the end to insert the extension before it hits the set screw. What will solder the easiest is stranded cable and this will provide an excellent and flexible extension.

Use soft wire for the extension rather than an allen key when soldering but preferably stranded cable.

If you are lacking soldering skills its a perfect chance to start learning. Failing that using a puddle of JB weld off the end of the needle with the stranded wire extension push through to the hole and the set screw.

Stranded wire extensions are the best and offer no vibration problems on the needle and its O ring(s).

All the newer OS AX's now come with this stranded wire extention which is fantastic.

John