Small, convenient take home 220-liter Nitrogen cylinders are available from iKegger. With a suitable flow regulator, this will provide 15min of gas flow, adequate for a peaceful death.. A large 1000-liter cylinder is also available from this same distributor.
Another source of nitrogen cylinders is Hobbyweld.
Note, however, the smallest cylinders Hobbyweld supply is 9 liters and contains 1,300 liters of compressed gas - much bigger than required. Hobbyweld cylinders must also be collected from one of their distributors as home delivery is not possible.