this is an indirect response to your question but one of the reasons people get hungry 60-90 min after eating breakfast is that their breakfast is too carb-heavy (cereal, oatmeal, toast, granola, fruit which your body burns immediately). If you buy a big container of full fat unsweetened greek yogurt for your fridge and take some nuts (or a bag of keto granola you can throw in your suitcase) you'll be consuming over 25 grams of protein and 20 grams of fat and you'll be surprised how long this keeps you full. Boil some eggs in the microwave the night before if you think you want even more food and eat it with an entire avocado in the morning -- you won't be hungry during your dive. Try this before you go on your trip to see if this works for you.
Or just heat up your leftovers from dinner and throw it into a tortilla with some cheese and you have a breakfast burrito. All of these options are way easier than wandering around at the crack of dawn in search of a restaurant but maybe you're an early riser and enjoy being up and about.