The Praxis Kit is under the last ladder at the very bottom of this elevator shaft. The only way into the shaft (e.g., not using the elevator) is to locate the place where you may punch a wall near the Heng Sha Court rooftops. It is the elevator shaft of the building where the Dutchman hacker was staying, but the enemy PMC is currently raiding. Be sure to buy both units before proceeding to TYM. The Praxis Kit is in the secret room hidden by that break-able wall. There's a break-able wall past this DRB guard station, which is highlighted prominently if you have the Wall Punch augmentation.
There is a DRB sewer checkpoint (crewed by three gangsters) near the ladder to the weapons cache (Jenny Alexander's side mission). Derelict Row Banger (DRB) territory sewers.The storage cage (3663) has a Praxis Kit. You can locate the passcode to this Level 5 door from a pocket secretary in an alley by the police station - or, if you have the ammunition and explosives, just destroy the door with weapons fire - if you cannot hack the door's lock. Locate the Purity First / Humanity Front terrorist staging room in Tindall's and O'Malley's apartment building (the one building with the locked gate).Be sure to buy both units before proceeding to Heng Sha (or earlier to FEMA).