Bike Bandit is a pretty good resource. They ship anything over $99 for free, and they offer discounts for things like military service, student, etc, but you have to call them to get it applied to your account. As far as finding parts, I always go to world of triumph, find the triumph part number, starting with a "T" usually, then search that part number on bike bandit, I've never not found a part on there.
The only caveat to bike bandit is shipping time. They don't stock parts, so it's all drop shipped from Triumph direct.