I'm having a hard time getting control rods, mainly the longer ones, i have used bicycle spokes but they are too heavy, shifter cables for the simple soarer, the train/model shop here in Utrecht only has 15cm rods of spring steel.
Some models need longer rods, i have build some models like the bloody wonder with the short ones and had to move the servos back and that added some CG problems. The store i have found now has the same rods but 100cm long.
Not MIG Wire. Use TIG welding filler wire. it is straight and should be found in 1 meter length's and many diameters plus it is available in practically any metal alloy you could ever want from steel to titanium.