A grab bar is a safety device that should be in every bathtub and shower stall to provide safe footing on the slippery surfaces in a bathroom. It gives a helping hand to anyone at any age or physical condition who requires assistance. Add a shelf to that safety feature and it’s a winning combination for a bathroom accessory that will be well used and appreciated. You’ll find them sold In a variety of styles and finishes such as brushed nickel, chrome and bronze sold at home centers and kitchen and bath retailers. The best choice is a shelf grab bar with a secured mount design that installs on any wall stud at any angle to assure its installation will be sound and stable.
Here's a link to Moen's shelf grab bars where you'll find more information and installation instructions called product specifications Moen Shelf Grab Bars.
A handyman will install a shelf grab bar for $136 which includes the labor and material. You can buy the accessory for $65 and install it yourself, assuming you have carpentry tools and experience.