Found another cap (original name "DJI4 lens cover_LenseGap.stl" no clue where I found it  this one: https://www.printables.com/model/1039265-dji-osmo-action-4-lens-cap) that fits action4 good and modified it a bit thickening the bottom for better protection and making it bit higher so there is a space between glass and bottom for even more protection...

Print in hard tpu for best protection6