sorry don't know where to get them but try remoulds not retreads they are safer and not much more. mate had low profile remoulds actualy good tyres raited to 140kph although he did 200+ chassing a motor bike
just my 2c
Reality is that they are VERY low quality.
They are speed rated to 'S' for a reason.
Lowlux, your mate is a goose, a0 for having retreads and b) for going that fast on public roads with reatreads.
As mentioned earlier, unless you car came from the factory with S rated tyres or lower, it is illegal for you to drive a car with them fitted, and moreso, for the tyre place to put them on in the first place.