Other sourches I use is mineral drops aka magnesium oil / chloride
The black salt. Both contain a good amount, the salt smell no good but the taste is to live with.
In addition to the food sources of course: what actually gave me the hint I needed more sulfur was an intense craving for aspargus. For one year I needed it daily. I then looked it up, found out it is very rich in sulfur, took the msm, and the craving slowly ceased. Still like it though, but not all the time.
The use of fertilizers are probably the main reason for the sulfur cycle to be broken.