I do not know of any other pre-war movies about nudism. In fact, there aren't many good and serious ones after the war, either.
There were a few interesting books on nudism published around 1930 on nudism. One such book is "Nudism in Modern Life." Another is "Nudism comes to America (I think it is) and finally, "Among the Nudists." They are all a little dated and quaint as well as deadly serious about the subject. One had to be deadly serious about nudism to admit it at the time, although they're still just about nude recreation, in the sense of "re-creating."
A more recent book that I highly recommend is "Turning to Nature in Germany: Hiking, Nudism, and Conservation, 1900-1940," which is a fairly academic book. But it tells you how it all got started.