An update of sorts. A couple of folks suggested cork. At first I thought I would at least get to open a few bottles of wine ( and may still). But a little searching turned up the fact that new, you-gotta-have-them-or-you're-not-a-real-racer-boy Zero Gravity brakes use Corima cork composite pads. They are red, which isn't too bad. The question is are they "carve-able" so that they can be made to fit vintage brake shoes.
Well, I've just ordered a bag of four from Competitive Cyclist ($25.00). Not exactly cheap and not as much fun as collecting wine corks, but perhaps a better solution. When I get them, I'll report back on how easy it is to adapt them to vintage brakes.
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Phil Sieg
Knoxville, Tennessee