To find Division Tech crates, defeat enemies in the Resistance arenas or explore them. Note that enemies in West Side Piers open world have a chance to drop Division Tech as well.
In addition to Division Tech, the Optimisation requires default currency credits: 250,000. This number will not increase, like for the recalibration station.
Furthermore, deconstructing High End gear, High End weapons, Gear Set items, Classified Gear Sets, Exotic armor and weapons now has a chance to reward Division Tech.