We have had good luck with those suction cup hooks that you've seen on those informercial ads on TV. We place them on the inside of the shower stall, push the hook on the wall and pull down on the hook which creates the suction to hold the hook on the wall. Believe it or not these things stay on, except over the winter when they all fall. Anything wet gets hung here.
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700