Frittata sounds good! I also make ham and egg tarts which are similar and really easy to make! Line muffin tins with slices of lean ham. Add lots of chopped mushrooms, onion, peppers, tomatoes, etc. to the ham cases. Top up with a beaten egg and sprinkle with a HExA of grated cheese. Bake in the oven until set and golden brown. Can be eaten hot or cold!
Also, sandwiches don't have to be out of the question, you can still have them! Use either a small wholemeal roll or two small slices of wholemeal bread for your HExA and fill it with lots of salad and meat. My favourite is a chicken blt - pieces of chicken breast, grilled lean bacon, lettuce, tomato and 1tbsp of extra light mayo, all just for 1 Syn! Or ham and pease pudding, completely free!
What about savoury rice (provided you like it cold)? Make it before you leave and take it in a little lunch box - all you need is a spoon and your set to go! Plus, if you add lots of veggies (mushrooms, peppers, tomato, etc.) it makes it even more filling!
Take little packets of lean meats, i.e. slices of lean ham, chicken pieces, etc. Completely free and something to nibble on if you get peckish. Also vegetable crudites such as carrot sticks, celery sticks, cherry tomatoes, etc. Again, all really good for nibbling. Pieces of fruit are also really handy, particularly apples, pears, oranges, etc.
Hope this helps somewhat, and hope you have a fantastic trip!