What about an ASO brace? IME it gives more support against rolling than any mass-produced boot could, while leaving you free to flex and extend the ankle. It's very low profile and fits inside most shoes.
This is a great brace. I had a trimalleolar fracture with 14 screws and a plate 3 years ago. When I was finally released from the walking boot, this brace is what my ortho gave me. It is indeed low profile, and gave me great lateral support.