Why don't you try this place in Pasing, a town on the west side of Munich:
www.fkkmuenchen.de
FKK Sudfass Oases
Entry: 55 euros
30 min: 75 euros
60 min: 125 euors
Open: 11 am - 4 am
...then give us a report!
Looks like you can take the S-Bahn most of the way.
Neptune