I dont know where you are at but, Look up a source for industrial water treatment. All chem, Nalco, Alltair, and US Filter are a few. Most of those places will sell a gallon of DI water. That is what we use as our standards in power generation(for testing meters,conductivity probes etc)
If I need any I just bring a jug in from home.
Of course it helps to work in the water treatment area of plant.
