Unfortunately, certainly in the UK, options have narrowed down rather than become easier or more convenient. SN is very challenging to obtain nowadays for most of us, so treasure what you have.
It's still for sale in 6.25% concentrations and not impossible to purify:
"Purification of NaNO2 can be achieved by making some
isopropyl nitrite with it (nitrate doesn't react here), isolating and purifying the ester and saponifying it by refluxing with alcoholic NaOH solution. NaNO2 separates right out, as its solubility in alcohol is small (3g/100ml in anhydrous ethanol)."
I'm not a chemist and I'm not sure why isopropyl and alcohol solutions aren't the same, but the process seems to be mixing and stirring.
I think personally, switching back to a helium tank is a better decision. I only recently heard about sodium nitrite and there's no purification of helium required...