Strong suction cup that may be used on humid environments. I use it inside the box of my bathroom, for more than 6 months and it still works very well.
Online store: AliExpress
US $5.2 30% OFF|Bathroom Suction Cup Handle Grab Bar for elderly Safety Bath Shower Tub Bathroom Shower Grab Handle Rail Grip-in Grab Bars from Home Improvement on Aliexpress.com | Alibaba Group
5.2 USD