The straps in the pix that Fred posted are very similar to the Dunlop straps. I have another rubber cable strap that appears to be designed for a seat stay rather than a top or main tube, but the design is basically the same. These are much more simple and not as nice as the Dunlop straps, but may serve as a model if someone wants to try to fabricate some. The Dunlop straps actually have the Dunlop name in raised letters on the strap. I don't think it would be easy to make these out of an inner-tube or flat-sheet rubber because of the "nub" on one end that is thicker than the rest of the material. This "nub" forms the reinforcement that keeps the end from pulling back out of the hole in the strap. All of that can be seen very clearly here and in the subsequent pix:
http://www.wooljersey.com/
I have listed the dimensions along with the pix. Of course, these
would have to be modified for a top or main tube strap.
--
Wayne Bingham
Lovettsville, Virginia USA