Try asking for "saltpeter", the same thing as sodium nitrate. Ask your
pharmacist.

Main Entry: salt=B7pe=B7ter
Pronunciation: 'solt-'pE-t&r
Function: noun
Etymology: Middle English salt petre, alteration of salpetre, from
Middle French, from Medieval Latin sal petrae, literally, salt of the
rock
1 : POTASSIUM NITRATE
2 : SODIUM NITRATE