I honestly can't remember the last time I encountered a severe enough backbow that required a 2-way truss rod. And I can't even count how many guitars I set up, repair and restore every year. Considering the expense I realized that they are no longer necessary in my build projects. So I'm now manufacturing my own 1- way truss rods, using 3/16" steel rod, brass bell nuts (for adjusting), drilled out and tapped, and 3/4" long - 3/8" bolt sections (for anchoring), also drilled and tapped. Its all thats really needed for a good playing guitar if its made right. I can make half a dozen truss rods for less than 5 bucks in less than an hour.
http://www3.telus.net/Alsplace/Truss%20Rod/