I used a button as a demonstration only.
Do note that you are now casting every frame due to the nature of UMG variable binding. This is a costly operation; while the cost is negligible in this very instance, when dealing with a 100 of inventory buttons, you’d want to avoid it and send ready data to your widgets. Or use Direct Blueprint Communication.
To avoid casting every frame and to keep the logic in the widget, Cast only once on EventConstruct and create a reference to the GameInstance in the widget (right click the VariablesAndFunctions and Promote to variable). Use the reference variable to fetch data from the GI.