If you need potassium, there is always Potassium chloride.
Available as a salt substitute in the supermarket, and in tablets at the pharmacy.
I thought that KCl, because, after all, is a simple chemical, asked the pharmacist (well, the guy in a labcoat behind the pharmacy counter) at Walgreen's for the OTC version.
"Oh, no!" he said, acting like I had just asked for morphine: it is a dangerous drug: they use in the cocktail of drugs they use for the death penalty.
And the next time I go to Publix, there it is, near the salt, made by French's, the people who make mustard, labelled "No Salt", for people on a low sodium diet.
So US law bans us from buying it as tablets, but if we want it in crystal form (with a few additives to prevent caking), we can buy all we want.
US Restricted drug laws make no sense and often seem to exist only to keep the prices of drugs high.
There is no R&D or development costs associated with something as simple as KCl.