I've plugged em before and I'll plug em again: Stibbar
I love em! Definitely wish I bought more! Yes they have collars, too. I love this leather. It is not bridle leather as requested: this is softer/more flexible and lighter which I prefer for my small dogs. The bridle leather collars & leashes I have seen are quite stiff and that transmits to small dogs. When the neck is only 10" the bridle leather seems to not break in much with wear.
Tory Leather makes nice collars and belts, reins. I have had belts and collars from Tory.
Gundog Supply makes a fair priced, good leather collar. I have the K-9 Komfort for mine(3/4" with brass plate) on my dogs now.