I had a couple car harnesses but ended up taking them both back. I could never get one to really fit Hannah right and they always seemed to pull over to the right, pulling on her all the time we were driving.

So I got this other type of thing its like a seat belt. One end is the snap and the other end is a seat belt buckle. You snap the end on any ordinary HALTER (never a collar) and snap the other end into the seat buckle. Works like a charm I love it.

I have never seen them in a pet supply store, I got mine at Wallmart. $15-$18 Canadian.