I use a magnesium foot bath every evening. I use the Ancient Minerals flakes. Epsom salts did not work as well. (I also frequently put epsom salts in my regular bath as well.)
I also used Mitoku "Bitterns" Natural Nigari as a source of mag chloride. <[naturalimport.com]
Four or five years ago, I had this brand tested at a local chem lab on their x-ray diffraction machine for heavy metals and it was clean (the results are posted in the archives here). Nigari is MgCl2 that the Japanese use to coagulate tofu. I works well to make "magnesium oil." I purchased a couple of 44 pound (20 kg) bags a few years ago.