I agree with you that having the ambient sound adds to the viewer experience. I guess the wind will be very problematic up there for the microphone. I presume you are using a Go-Pro, I did a quick Google and came across THIS. I don't know if you've seen them before. I would be inclined to think they are not much better than the things you have already tried.
The most affective method of wind noise reduction is the zeppelin type with a big fluffy around it. Having the gap between the "dead cat" and the mic makes a big difference. I don't see how you could have an arrangement like that with a GoPro unless you had a separate microphone or sound recorder.
There will still be some wind noise which you could perhaps mask with a little light music.