Mikashima made some pretty beefy nonlaminated leather straps. They were sort of a thicker version of a Binda with nice hardware and metalic gold letter stamping on the strap in a number of colors. I think they came on a fair number of higher end Japanese bikes in the 70's and early 80's. Where to find them now is a matter of luck, or maybe Dennis Young knows a source.
Chris Van Scoyk
Ankeny, IA