The pH of NAC is very low, highly acidic. I would recommend to mix Sodium Bicarbonate 500mg to neutralize the pH to 7.0. I take this in conjunction with Vitamin-C 500mg pure form so that I can neutralize both NAC and Ascorbic Acid at once without further excessive sodium intake.
It is the cheapest Cysteine I could find, however when you buy it, you have to consider how to ingest your daily docis. For medical reasons I need 4.5 gram/day and that's a high docis. When I dissolve the powder in water and drink it as quickly as possible, I can feel my teeth get rough. I assume the HCL-form has a very low pH and dissolves a tiny layer of the teeth. It also has a horrible smell and taste. First I tried to neutralise the acidity with CalciumCarbonate powder, but that seems to result in some chemical reaction producing H2S (smelly!). Then I got it down by wrapping small heaps of cysteine powder in a small bits of toilet paper and swallow it quickly with lots of water, but this is not a nice method. A pill-filling machine would make this product far more convenient.
However, I recently discovered that mixing it in only 3 spoons of fruit-yoghurt, makes it taste quite okay and that is the best way to ingest it.
Good luck to you!