Tiggeroo,
This is probably too late,as by now you've gotten to the store. (I haven't been around lately.) But for future reference . . .
Cooked Icing (my favorite - it doesn't seem as sweet as those w/10x sugar)
Cook together:
3 Tbl flour
3/4 c milk
Stir constantly until thick. Cool.
Add:
3/4 c butter
Beat 4 minutes, then add:
3/4 c sugar
Beat 4 minutes, then add:
3/4 tsp vanilla
the cooled flour mixture
Beat until smooth. Refrigerate until spreadable.
I don't know how this one would be for banana cake - my grandmother always used it for applesauce cake & it was
wonderful!!!! It gets hard & can be picked off & eaten separately, too.

Caramel Icing
1 Tbl butter 2 c brown sugar
5 Tbl milk 1 Tbl vanilla
Combine all ingredients in a saucepan & stir until sugar dissolves. Cook syrup for 2 minutes, stirring constantly. Cool until you can hold your hand on the bottom of the pan. Beat 2 minutes & spread on a reasonably cooled cake.
Deb