Smoldering Brand procs at L1, decent ratio, and drops like candy from the hole (so it should be relatively cheap to acquire).
Do note, however, that stun and debuff procs generate more aggro than simple DD or DoT procs. Therefore, the two weapons you have (stun for 1 proc and -AC for the other) are about as good as you can get until dual-stun
SSoYs that start proccing at L37. The market for SSoYs has dropped dramatically even though their aggro is still great into the planar levels.
Not that I know a lot about warrior tanking, but the advice already provided looks decent.