Try Magnesium Sulfate - Epsom Salts.
It has the highest absorbability, and it is extreamly cheap. Keep away from your times of calcium intake because it interfears with absorbtion.
Note take a dime size or less amount of crystals in your hand about once or twice a day. If you start noticing laxative effects (what magnesium does in high amounts) just cut back a bit.
Note: Magnesium in this form was helpful for kids with ADD and ADHD in a Polish study(hence why I use it). Just do a Google search for it.