I've personally had luck with Istanboa. There's several times where I've come across 2 Antiquities, and it's usually an out-of-the-way place so that you can just hop from quiet realm to quiet realm. There are other areas with 2 Antiquities, but I don't remember their names off the top of my head.
Best places are Thieve's Den, Caravan, and ... everywhere else. Seriously. It spawns in every area of Mirage, you just have to take note of those areas and then return to them in a systematic way.
Just log in late at night or early in the morning, make a run through the entire area you've decided to farm and pick up what you find. Hop realms. (You know how to change realms, right?) Sweep through again, making sure to go back to any area where you've noted Antiquities spawn. Repeat until you get what you need.
I need them for crafting the new legendary wands, they usually spawn here and there but is there a good place or boss to farm them?
I've given up on the Bazaar completely btw.
Anywhere in Mirage, you'll find them. I usually get them in Caterwaul, Rubal Wastes or Thieves Den. No need to fight bosses ( I don't think they drop them ).
The two main places I check are typically Akai Borrows and Rubal Wastes... Otherwise there is one place you can check (rare) but it works "Thieves Den"