I believe you need to get the schematic or module crafted/created by a Musician (at least a Novice Musician... NOT an Entertainer, I believe)
Lt Charinida D'Aoyama of the Imperial Inquisition
Master Merchant, Master Droid Engineer, Master Weaponsmith
Custom Droids, Melee, and occasionaly XG Mines/C12.
No Ranged weapons. Well, maybe Scout, E11s and T-21s.