Magnesium sources and bioavailability?

I used to get my magensium from nuts and seeds, but those are difficult to tolerate now. Same goes for nut butters as they'll go right through my colon.

I do eat canned spinach everyday but it doesn't seem to be having the same effect that nuts did. Are topical lotions and epsom salts the answer? I am unsure about the bioavailability of those, since the studies are not conclusive.

I also use Magnesium oil on my neck and cervical region, because that is the point where my migraine usually starts, so for the sake of relaxation purpose.
In addition to that, I take Mg-Citrate tablets, Vitamin Shoppe Brand, 600mg/day, for relaxing blood vessels, again for migraine issue.

I am sure, some of it gets absorbed in the system.

I'll try out magnesium oil. Has anyone had success with epsom salt baths? I do have some cocoa butter laying around - wonder if it works topically as well?

Cipro knocked out my sleep a few months back and I've come to learn that its mechanism depletes the body of magnesium. I used to be in the therapeutic range but I'm not sure it is now because of these aches and pains I've developed.