Get an exotic engram and exotic cyphers, go to Rahool and go to the focused deciding page. Tab over to the second page and grab it. I’ve been doing that with all the exotics I don’t have so I can get them to drop, been making a lot of decent builds with them

Is the focusing option available at Rahool for you? And I think LSs still might drop older exotics. When you however over it in collections does it say anything? Also, if you have access to Lightfall or Neomuna I think Vex Strike Force, which is a public event that occurs in the Vex incursion zone. Finally Xur... check him every weekend, you can use a stat focusing mod on you ghost to possibly change the archetype and split... it doesn't always work. Even if it doesn't change, it will unlock the exotic for you. Other sources for exotics. Xur Sells 1 per week. Chronologs if you have those. Keycard rooms if you have Renegades.