Optimal cooking tool for long-duration steaming
If you search "multi cooker" on Amazon, you'll see a multitude of devices similar to the one you linked and the vast majority of them are able to do what you're asking. Another option that would defintely be worth considering since you're already accustomed to preparing the sort of dishes you're wanting to make with your rice cooker is upgrading to a higher-end Japanese model such as the Zojirushi Umami. I own a comparable rice cooker and it's probably my favorite small kitchen appliance. It also seems tailor-made to do exactly what you're saying you want to do. It uses an array of sensors to slow-cook/steam to perfection and automatically enters a 4 hour keep-warm cycle when the cooking is done. You can also set a start-timer if you need more time and want it to wait a while before it starts cooking. 

As an added benefit over the multi-cookers, you'll also be able to effortlessly prepare rice that comes out so indescribably perfect that even the rice at an upscale Asian restaurant won't compare to what you can make at home with the touch of a button. That's Japanese design for you; when the electronics capital of the world also happens to be a place where pretty much everyone eats rice daily, their engineers are going to produce one hell of a high-tech rice maker.

I apologize in advance if this answer is deemed inappropriate; I understand that answers aren't supposed to just be opnions, but there are many different methods and appliances/tools that could be used to accomplish OP's goal and no objectively best way to do so. Anyone's suggestion would probably just be based on what they'd do in their own kitchen.