You can make your own. Using a super magnet like the ones from Lee Valley, glue it to the underside of an appropriate container. As long as you put it down on a steel surface, it will not flip over. I do have a Spill Master cup at work, but I use a wide mouth plastic container that is as wide as it is tall, with a screw cap to seal when not in use. Reason I use this, is the opening on the Spill Master is small when you are dipping and operating the machine at the same time. Too easy to miss.
Pierre