The leather carrying strap I fashioned out of an old belt has worn in beautifully. I treated it with leather saddle goop once, and it could probably use another coat soon. The leather has stretched it a very attractive way, nicely matching the contour of the chainring I think. The washers have kept the leather from tearing, despite some initial pinching which can been seen in the photos:
If the leather continues to stretch I may elect to flip the strap around and resize to fit more taughtly between the front and lower rear screws.