Inside cardboard box in roof space - access via vent on top of arch outside or via the hatch inside. Gain the key from Vadim Orlov - located in a building in the alley next to TF29 at night - and unlock the vault to find the Praxis Kit. One more Praxis Kit can be found in the Tai-Young Medical Vault in the Executives Vault on the bottom floor. Hack the keypad to open the safe, or use code 0310 to bypass the lock. There is another on Level 1 in the Executive Safes Room B, stored in a Security Level 5 safe labeled B07. Open the room by interacting with the nearby sculpture (raise, turn, raise, turn, turn, raise) and open the level 1 locked safe inside. In the CEO's office at the top floor of the bank, there's a secret room. You can find it sitting inside a cardboard box on top of the ceiling kitchen cabinet. Near the Pilgrim Station, enter the top floor of the complex and enter apartment 96. Above the sink along the top shelf is another medical box among books that holds the kit. Inside Task Force 29, head into the infirmary building on the first floor, and look for a table counter to the left of a locked storage area with a sink and medical box. He will sell another one upon returning to Prague at night, and one final kit during Prague under curfew. Two are sold by Tars the arms dealer on the second floor of the apartments (10,000 credits each). One floor down from Jensen's apartment, you can find a Praxis kit inside a stash hidden in the floor of the unit with the eviction notice on the door. Open the level 3 locked safe to get the kit (Passcode: 5555)
There is another located in Koller's Dungeon - locate a moveable painting by the elevator hiding a vent leading to a gassed room.