A.H.
We like Udi's brand or Rotella brand GF bread. I have never made pie sandwiches like you describe, but we have toasted, grilled it (for grilled cheese) and also made French toast with these breads and they are as good as regular bread. You should be able to find either brand at a local grocery that has a natural food section, Whole Foods or Trader Joe's. Good luck! Those sandwiches sound yummy!
Happy Camping!
A.