There are no harmless ways, because the main function of constriction / dilation of the pupil is adaptation to a change in light mode. Accordingly, if there is a bright light, and your pupil is dilated, your retina will not be happy.
Well, with a constantly dilated pupil, it will be impossible to focus normally on anything, which again will cause discomfort
If the goal is to visually emphasize the eyes, then you can use special Korean contact lenses. They do not enlarge the pupil, but the entire iris.
there are no absolutely harmless and episodic ones (both atropine and tropicamide have a number of side effects besides the logical photophobia, and light drugs do not have a lasting effect).