I wouldn't be too hasty. You could make your own wonder bag from an old duvet. I don't think the wonder bag was made for cooking on the move ~ you would need a container that doesn't spill. Maybe use a pressure cooker (dual purpose)?Thanks for that @Cat53. I very much like the idea and will most likely buy one in preference to a slow cooker. The idea of cooking while travelling is brilliant. thanks for the heads up.
Mr D's will be better at keeping the heat in, and cooking. But it will also be more expensive.