I've seen small cans available from gunsmithing-supply places like Midway USA and Brownell's, but their prices are pretty outrageous. Kroil started out many years ago as an industrial-use only product, so it's not readily available over the counter. I learned about it in the Air Force, where every base worldwide kept it in stock. The website is by far the best place to buy. I buy mine in 1-gallon quantities!
Jerry