Hi there. You can pick up 2 guaranteed Techsec armor pieces from Zavala each week by completing weekly seasonal hub challenges. The recent 300 power catch up chest added next to Zavala also gives a full set of Techsec armor. Besides the guaranteed sources, Techsec is a random world drop from activities, chests, enemy kills, and a few vendors like Hawthorne. This includes the bonus drops from portal activities. Once you've acquired everything from guaranteed sources, the way to farm more is by simply playing until you get what you're looking for. If you want to suggest a different way armor can be acquired by choice, then we recommend creating a topic in the [url=https://www.bungie.net/en/Forums/Topics?pNumber=0&tg=Destiny2%20FeedbackD2&tSort=1&tType=0&d=0&lang=en%3Freload%3Dtrue]Feedback forum[/url].