Not sure what you are asking about here, but here's an attempt to answer the basics.

Cutting threads is usually done (by home mechanics) with a die turned by hand with a handle/holder. (If you buy a tap and die set you get several sizes of both and the handles to turn them) You need the proper size rod for the thread you are going to cut.

The steel you are going to use makes a big difference in both the job and the final product.

You should check with a mechanical engineer. They would probably recommend/use a "stressed tool steel." This kind of steel is relatively easy to obtain and machine. They might recommend an alloy depending on the look you want (and the tensile strength you/they want). Not sure what the minimum diameter available is (or what the linkage size is) for stressed rounds, but I think it is pretty small.

Yes there are separate dies available/necessary for left or right thread. As you have figured out the piece you're talking about is a turnbuckle with right hand thread at one end and left at the other.

I know the piece you're talking about and if it were me, I'd take it into my local ACE Hardware.  They have 3 or 4 older guys there that can make pretty much any simple item you need in the little shop in the back.  I'd probably just use a stainless rod and make a spare while I'm at it.

But yes, it does take a die specifically made for lefty threads to cut those.

Instead of having a whole new rod made how about having a short rod made that has right hand threads on both ends that are the same as the orignal and have a threaded coupling made to connect the two rods. Or      just cut the rod and weld a longer piece in. Probably simpler to take the stock rod in to a machine shop and have them make a longer one.

That is one item that I'd have thought to be included in the forward controls package....and what average person has the needed metric dies in their toolbox.  I believe the threads are 6 x 1.0 MM threads with one left and one right hand end.  

You can have it cut and rewelded or have a new one fabricated, but I wonder if there is another cruiser with a longer linkage that would fit.  Just a thought.

I am a cheap basturd I would go to lowes buy a SS left and right thread to match my needs and a length of same dia rod. cut the bolt heads off and cut the rod to the size I need and mig it all together, but then again I work at a plating/machine shop and can grind it true blast and chrome it when it is done. Just my thoughts 8)