FORETHOUGHT IS THE KEY!
Oatmeal and cinnamon mixed together in a large ziplock fits easily in a suitcase and is a perfect gluten-free breakfast in a pinch. It can be easily prepared in a hotel room microwave, or simply with boiling water in a cup.
If you can fit them, bring snack foods such as healthy, organic chips or popcorn. My program prevented me from eating anything raw (including nuts, a food normally allowed on a gluten-free diet), so I was truly challenged for snacks! At home healthy blue corn chips fit the bill, but finding anything other than highly-processed, GMO-filled brands prevented me from having anything to snack on. Next time around I will pack my own. Preferred brands are Garden of Eatin' or Late July.
A package of gluten-free spaghetti took up no room at all in my carry-on and saved me for two meals. Out of the USA, gluten-free is not as readily available in restaurants, if at all. With a small kitchenette in our hotel room (often an option overseas), I was able to cook up some pasta when truly in need.
Finding a small local grocery and shopping for our hotel room made all the difference to my days.
Rice cakes have added a new dimension to my diet. Prepare with mustard and local cheeses as a packable sandwich, or with spreadable nut butters as desired. Be sure to purchase foil and ziplock bags to wrap and transport your own lunch foods so you don't find yourself in a bind. In addition to local cheeses and nut butters, also purchase condiments, plain yogurt, fruits and vegetables, and eggs (for hard boiled eggs, if you have the facilities to make them), etc.
3 - Contact local restaurants ahead of time.
I was surprised and touched by the willingness of local chefs to accommodate me. They wanted to know my specific needs, overcoming language barriers to help. And they truly did, so this is worth a try. Just send an email in advance. Smaller, local places are your best bet.
4 - Don't forget to plan for the airport and in-fight meals!
I purchased tupperware at the local store and prepared my own dinner for the flight home. Good thing, as we were delayed four hours! I also had a cold bag (same kind you can buy here in the states) filled with local cheeses and fruit.
Traveling in itself is a stress on your system, the last thing you want to do is forgo the foods that work to keep your gut functioning optimally. Drink lots of water and try to stick to your plan. Give yourself a few days upon your return to re-acclimate yourself to being home by eating gently.