I have a great substitute for bananas that should work since they are cousins
of bananas: plantains. They are very banana-like in both texture and taste. I myself have a (minor) allergy to bananas, and have never had a single problem with plantains.
Of course. there are some things to consider:
--you may not have plantains in your area stores.
--you may be allergic to them as well.
--they may not actually act the same way as bananas in your recipe. I don't bake, and have never cooked with plantains, so I can't comment on this one.
But that all aside, I can think of no greater substitute for bananas then the mighty plantain.