The thermoplastic (who knew?) pads melted right off my long-reach clamps while calibrating those thermocouples, leaving the thermoset (who knew?) clamps behind. I tried a few of the obvious candidates for the job with no success, but (while fiddling around with something else) I came upon an unopened tube of Permatex Ultra Copper copper-loaded silicone gasket glop.
The cured silicone rubber is very flexy, which is sort of what you want in a pad, even if I’m not convinced they’ll stay in place. They seem securely mounted in the recesses of the pad tips; I worked the glop in with a screwdriver tip.
Those blocks were spares from the cartridge heater escapade.