Contact Lori Apthorp, at
Uke Leash
She's a member here, and responds quickly.
I have several of her uke leashes, and use a leather one on my Donaldson Custom Concert, with the strap button adapter. Great Strap, about 1/2" wide, and will last a couple of lifetimes.
Of course, the polyester ones will too, but I really love the leather with my Donaldson.
-Kurt