I've never found potassium in sufficient quantities in pill supplements - but low-sodium salt gives you 500 mg per 5g teaspoon (and another 1000 mg of Sodium, Ironically)
Thanks! Really appreciate the recommendation - I'm going to hit up all our local stores for some. Went jogging this evening, and for the first time in about 2+ months didn't get any cramping in the legs (which happens to me 100% of the time for any run longer than about 8-10 minutes), and the only change I've made is supplementing potassium, calcium, and magnesium.
In keeping with this thread - I guess I could vary different dozens of variables, one or more at a time, apply the same Ketosis machine learning algorithm, and see what really makes the difference.