Ellis,
The Leica is called a wrist strap, but this type of strap is more commonly called a hand grip strap.
I used a Hasselblad hand grip strap on my Canon 5D MkII, which was very comfortable, but have abandoned Canon since it stupidly refused to come out with a higher megapixel camera.
It seems the Hasselblad hand grip strap is no longer made.