Hi it is best to keep babies with eczema cooling as much as possible and out of the sun. You may have to adjust your travel itinerary for baby.
For sunblock you can consider getting a chemical free sunscreen and uses mineral based ingredients like zinc oxide or titanium oxide. It should also be fragrance free and alcohol free and of spf 30 at least . Test a bit on baby wrist first before a few days before applying.
You can try brands like
California baby or Neutrogena for babies
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