Does anyone now where you can purchase this.?
A great way to get magnesium that avoids the gastrointestinal issues and horrible MgCl taste is to take it transdermally. You can rub a concentrated mix of "magnesium oil" (magnesium chloride plus water) on your skin. But at that concentration, it's likely to sting.
A better way is just to buy Epsom salts (magnesium sulfate) in bulk, or magnesium chloride in bulk and add it to bathwater.
Both magnesium chloride and magnesium sulfate are sold in small amounts in expensive, trendy bottles on Amazon, etc. But these are actually dirt-cheap industrial chemicals that are best bought from aquarium supply houses.
The most well known aquarium supply house is Bulk Reef Supply:
http://aquarium.bulkreefsupply.com/search?w=Magnesium &asug=
This bath is best taken before bed as magnesium's calming effect can make you a bit sleepy.
If you're a cheapskate like me, you can economize by making a more concentrated water+Mg mix and applying with a clean sponge while sitting in an empty bathtub.
But injecting magnesium strikes me as expensive and needlessly fiddly.
Dr. Axe (DC, not MD) has a good article on foods rich in magnesium. Magnesium is an essential part of chlorophyll, so dark green leafy vegetables are a good source.