We recently got a timer to go in the shower, as we are likely to be having water restrictions soon. 

So I quickly designed one in Onshape to allow us to mount it on the inside of the shower

Here is the Onshape link to the file, for if you want to make any changes

Shower timer holder | Part Studio 1 (onshape.com)

I printed it in Esun PLA+. I used supports, just for the hook part.

It only took about 15 minutes to print