Super ATV will be the most reasonably price route and there stuff is pretty stout. I have been running their trailing arms for over 2500 miles with no issues. Friend runs the Super ATV front arms and he has smashed into lots of stuff and they take a beating.
If you want to spend a little more money then:
CT Raceworx
S3 Powersports
Lonestar Racing
Long Travel Industries
all make quality stuff that are race tested.