Just to throw another option at you. There is a liqueur called St. Germain that is made of elderberry flowers. The stuff tastes a lot like grapefruit if you ask me. You may be able to brew a low alc. beer and then add the liqueur to it at bottling to add the flavor and some more alcohol. This is probably not what your after and I imagine would leave the beer with a thin mouthfeel but it is an option if all esle fails.
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