craft foam would have been my 1st suggestion (easy to cut to shape, bunch of different thicknesses....)
neoprene? rubber sheet? silicone?
you can probably buy a roll of gasket material for vehicles, usually a cork or a synthetic material with similar characteristics.
with drones they use a flexible filament called TPU. they picked it because of it's flexible (won't break/crack, etc..) characteristics. it's used as canopies, motor spacer/mounts (to reduce vibrations).
might be tricky to get to print initially (probably have to make adjustments to setting or printer)
check durometer harness between what's typical with gasket builds and what TPU filament is.
