I've been trying to find a source for justice points ever since dinging 90. I've had horrible luck with int plate drops in normals (and no justice from those either...?) and the one int drop I have seen was ninja'ed by the tank.
I don't have the time to play all day like most of my guildies, so they are way ahead of me and apparently VERY busy knocking out heroic achievements and challenge modes.
As I started with a monk I have no 4k JP cushion coming into the expansion. While leveling I did some instances, but overall I reached just below 1k justice points, not enough to buy anything.
So scenarios award VP, dailies award VP.... Where do I get JP? Don't get me wrong, it's nice to collect VP, but I really would like to know if there is a source to get JP at the moment.
Whoops, overread that.
Hm, not sure then, sadly. But just for entering them you could basically take any item and hoard it in your back.
Also, questing through the various zones (Townlong and Dread Wastes) will give you at least a few 442 and 450 items.
You could also try scenarios. Arena of Annihilation offers a quest with a 450 weapon as a reward. And after completing random scnearios you get a cache that always offers around 30 gold and may offer blu 463 items - sadly only for your class, not your specc.