I would agree with G, they came with leather straps that tied up the canvas while not in the lower postition. Anything else would be a fine invention of the owner.
David a friend in CA has patterns as he is on his second CE restoration. He uses leather dog collars that match acually really will, and look nice to boot.
Some really good examples...
http://www.flickr.com/photos/neals49/collections/72157602074152943/Neal,
