I supplement with a mag/potassium; the one I use amounts to $.18 a day; not all the potassium I need but it supplements.
https://www.amazon.com/NOW-Magnesium-Potassium-Aspartate-Capsules/dp/B000XHD0W0/ref=sxts_sxwds-bia?keywords=NOW+potassium&pd_rd_i=B000XHD0W0&pd_rd_r=6b7ccb51-7d30-4d79-bcdf-dd340b9ce3a8&pd_rd_w=JCkvZ&pd_rd_wg=tItWo&pf_rd_p=b0a9...
As for Magnesium, my doc told me today that Aspartate is the best form. This seems like a good one.
Has anyone tried using a combo supplement? Looks like NOW has one
NOW Foods Magnesium and Potassium Aspartate with Taurine, 120 Vcaps https://www.amazon.com/dp/B000XHD0W0/ref=cm_sw_r_cp_api_OYQDybS46T43F