In the Mission to support Aria's leadership over the merc groups: how to solve the Blue Suns mission without Killing General Oraka? He askes me to get him some weapons in return for leaving the Blue Suns alone. Where do I get them?
Kannik, one of the Salarian merchants nearby, will give you the weapons, but you'll have to bring him some artifacts. You'll find him next to the the Cipritine Armory kiosk, which is in the upper right corner of the Presidium Commons map.
We covered where to find the artifacts themselves here: