"suicide knob" is a classic device I've seen before. They were popular in the 60s or so. Named as such because they had a knack for snapping off. It's still in use for people with various disabilities. However, it's not especially hard to steer with one hand. I probably went 4 years after the driving test using only one hand with a palm spin. But then I got a car with a slightly slicker, heavier steering wheel and it didn't work so well.