Spandit, in the second message i meant "non treaded", or "smooth", obviously.
Flat soles ( in the meaning "leveled") logically have better grip than shoes with heels due to the bigger contact surface (consideration made appart from the material or thread pattern).
For the moment the quest is over for me.
I luckily stumbled upon someone who was selling his brand new byteks cobra boots.
Quality leather and construction, grippy and flexible, waterproof in the streams for now, even without wax, and lightweight at a bit less than 600gr per shoe, i’m happy with them.
And finally I'll have some time to make my own moccassins to which I'll add treaded soles, which should be nice too.
Thanks everyone for your proposals
Edit : spelling