What kind of bread lasts long?
The classic "long-lasting bread" is rather like a very hard cracker - ship's bread or pilot bread. Otherwise flour and yeast (add water and bake after it arrives) would be more suitable.

At some point when I had been reading too much old sailing tales I made some ship's bread - it's about as awful as the tales tell, once aged a bit (it was fairly edible, though fairly dense, when fresh, actually.) The commercially produced "pilot bread" is a bit more friendly for eating.