You are referring to a Focke Achgelis Fa330 Bachsteltze (Water Wagtail). Designed to be towed by a surfaced U Boat to give an extended range of view.
There are a few of these to be found in UK air museums. I would have to look through some books to come up with a list. If you are up for a bit of research, l would recommend that you start with a recent copy of Wrecks and Relics by Ken Ellis