JMH, I would like to suggest that you look for asbestos linings. Although asbestos friction materials have not been manufactured since the early 1980s, they are still out there.
When I replaced the "organic" brake friction materials on my street rod with asbestos it was like adding a power booster. Also, asbestos is very easy on drums.
I live in a relatively small town in Northern California and even here there is a brake parts supplier who can still get asbestos friction. I have also found it NOS on ebay.
