I did a quick check and I couldn’t find any compatibility data for cyanuric acid either. The concept of using compatibility data from a surrogate like cyanic acid when one cannot find data for a chemical of interest is sometimes acceptable. The "degree of acceptability" depends on how similar the chemicals are and what degree of risk one can tolerate. In this case, I would probably advise that some laboratory test be designed and run to generate specific data for the combination of cyanuric acid and 316 stainless steel.