I did extensive research on trailing arms before deciding what to do when I put viper trailing arms on my MM. All aftermarket ones are junk, and it truly is you get what you pay for. I ended up getting stock viper arms and paid $300 for them used, but with all the hardware on them. Now if you buy a brand new one you will need the bolt bushing and have it pressed in and the spindle bushings and metal washer for the bottom, that's another $15-20 for some oem parts to throw on it before its ready. I discovered ronnies this fall and have been very pleased with their service. Anything from yamaha is 3-4 days to them as long as the regional distributor has it. I got my chain case parts from them when I geared down and needed a shorter chain last month and to rebuild the tensioner because the bearing was shot and the roller egg'd.
The light weight ones like fabcrafts, mpi and alternative impact are cro-mo but the cost far exceeds what oem is even brand new. If you need a trailing arm, I'm in mass and have my old set still.