I have a "car desk", which is just a little expandable contraption you hang on the steering wheel, then you can place your laptop on it. I wouldn't call it ergonomic per se (the right external keyboard could probably fix that), but using it for about one hour per week, it works well and doesn't cause any issues I'm aware of. The driver seat is not a place where I previously could get any work done, so the bar is a bit low.