Hi MB
I use these
Endura Road Overshoes, and they are brill, made completely of Neoprene (wet suit material), they never let in any water at all, and keep your feet warm, and the 2 stripes down the back are extremely reflective in the dark.
I did buy some cheaper DhB ones, very poor, they now gather dust, in fact dusting with is all theyre really good enough for.
John