Okay...so, using the advice above, today I mounted the soap dispenser to the shower wall using command hooks. All that remains now is to stress test it. I'll give another report after we do that.
Don
Left to right: the wall bracket that holds the soap dispenser, 16-lb command hooks, and the soap dispenser.
Command hooks adhered to the back of the wall bracket.
The wall bracket adhered to the shower wall using the command hooks.
The soap dispenser with the lid removed. It can taken down from the wall bracket for travel, or for cleaning.
The soap dispenser mounted to the wall bracket.
Longer view of the soap dispenser mounted to the wall bracket.