This is what I bought although I did not research how many, in this strength, would be necessary.
I ordered from Amazon.
Ya, it's the CDC, I know, but here is their web page on potassium iodine:
That is sold by Walmart, too. But if you look at the back of the bottle of the one you bought, it misspelled healthcare once, which is a red flag for me, and I ordered something else.