FWIW, I have found Xylene is not as aggressive as Toluene. I concur with Jim as I have used Toluene on a couple of hypalon glues with good success. In fact, I have found toluene the most aggressive of all the common solvents but I am not surprised to hear that it is unavailable in California
Given it's reported health
risks, I remain surprised that it available retail anywhere
these days but it is!
It is one solvent I try to avoid and treat it with great caution, supposedly it penetrates the skin like water
through a mosquito net!
Anyway, hope you find something that works.