I use little strips of closed-cell neoprene foam. The idea being that the gas inside the closed cells will expand/compress as needed. No idea if it will
work or not but time will tell! There is not much room in the Casio’s I have done but the two analogue quartz I have now done have room for a good sized strip.
NB I tried to make sure not to squeeze the foam too much when placing it - otherwise a bunch of the closed cells will burst.