Low-sodium alternatives for Asian cooking sauces?
Unfortunately, the sodium chloride salt is a requirement for the fungus and brewing process which goes into making soy sauce. You are extremely unlikely to find a much lower-salt soy sauce; however, experiment with vietnamese cuisine which uses more chili and less soy.

If you can tolerate some sodium, this is the lowest sodium soy sauce I can find: Kikkoman less salt soy sauce. It has 3.4g sodium per 100ml, which gives 170mg per 5ml tsp, around 6% per tsp or 18% per 15ml tablespoon. (These percentages are based on the US and UK sodium recommendation of 2400mg per day, or 6000mg of salt.)