A snack that is rich in protein, low in calories and has a bit of fiber.. I would recommend a small platter that includes mixed fruits, vegetables, and some meats as well as nuts.
Almonds are actually full of protein and good for you, there's plenty of fiber to be found in dark cherries and even celery. Celery has no calories, pickled cucumber (dill pickles) also have zero calories but can have a higher sodium count.
Good sources of iron and protein include most meats, I recommend going to a local deli and asking about some of the various meats they have there that would go well with your snacks. Also some cubed cheese would go will with your meats. But everything should be consumed in moderation and smaller portions.