Mounting a heat sink on a S202S02 SSR
This package appears to have insulation around the mounting hole built in, so a metal M3 bolt should be acceptable without a separate bush. To confirm this, look at an actual part to verify that there is a sleeve of insulation around the bolt hole on the heat sink side; the data sheet drawings do not explicitly show that. However while they explicitly recommend an insulation sheet, they make no mention of a bush, so I believe they are designed for use without one.