Whatever you do, don't acquire a full size nitrogen cylinder ! Not only does it last for years of filling, and is a more stable gas with less pressure fluctuations due to temperature, and contains no (or minuscule amounts) of oxygen therefore won't corrode the inside of your rifle, and isn't volatile if in contact with oil, and is as pure or better than breathing air, and is a truly inert gas.
And if you do use it don't tell the "experts" on BBS that they're full of crap and don't know what they're on about and they need to speak to someone at one of the gas distribution companies, preferably one that produces the blasted stuff in the first place.
Otherwise you'll get banned as well
It works out cheaper as well