I bought a house and the shower had no mount for the shower wand, so I made one. You can attach a double sided 3M tape or screw it in. I recommend using the 3M tape to not compromise your shower water tightness, but the screw hole is great for an outdoor shower when mounting to wood.

Lowest inner diameter is 22 mm and largest diameter is 26 mm.  Height is 37 mm.

This design is Public Domain. It's was very simple to make.