You don’t need aqua panel behind shower panels unless using the very thin 4-6mm panels .
My shower unit uses flexi hose connection so install was easy .
Just connect and hang on brackets.
So the problem is self inflicted, you are causing the damp by drying in the home ( regardless of where it is) you have inadequate ventilation, a disused chimney must be ventilated . You don’t condensation in a warm ventilated property.
They are particular to that Dutch web site, unlike most cam fitting they are exposed and fit thru the frame rather than being screwed into one side.Doubt they will be available to purchase.