The brand I take is only for Scandinavia. But the ingredients are magnesium citrate, magnesium malate and magnesium lactate, + silicon dioxide. In a gelatine capsule.
Try taking magnesium citrate / malate with vitamin C (ascorbic acid) and little borax, cosmetical grade. This is one of very few supplements I can take even right before bedtime without food, never any irritation.
Magnesium ascorbate is an option of course. Took me long time to find out of magnesium :-)