Does anyone know where to get small cylinders of nitrogen
or argon gas to use in food preserving? Jars of dried
herbs can have the air displaced and replaced with inert
nitrogen which protects the material from oxidation.

But I can only find huge cylinders on the Internet, and
those companies are only interested in corporate clients.
I also saw liquid nitrogen used to kill insects inside
walls; it either suffocates them or they can be killed as
they exit the wall while fleeing.