Walmart, Sams, whatever. They are readily available locally, and online. Two minor things: 1. they might make your urine burn if you are taking too many. Just cut down and you will notice a difference. 2. THEY REALLY WORK. Check your sugar frequently to make sure it is not going too low. Cinnamon has no toxicity that I know of, but the blood-sugar effect is something to watch. I took two twice a day until my sugar got down into the lower range, then gradually eliminated one cap at a time. Now, one in the morning seems to do the trick.
More has no additional effect.
BTW, you have to build up a certain background level ~ this stuff takes a week or so to wear off such that you'd notice it, and a month before there is no more effect.
First time you use it, though, you may very well feel tingling all over your body.