Pre MkIII rear wheel buffer replacements

Anybody tried making a replacement for the useless rockhard buffers on the pre MkIII hubs? Any number of compounds out there look like attractive alternatives. I'm going to try using something cut out of the sidewall of a car tire and see, but if anyone has tried something that worked then that would be the place to start. I have a lot of money in a rebuilt gearbox and I think something as simple as this could make a difference. This would be one of the areas where the MkIII as it all over the previous models.