Try the GridSearch widget package here from the GitHub repository here. This is the latest version of the Grid Search widget available in the app store.
Copy that MPK file into <your project>/widgets, and press F4 in the modeler. I believe the "Dropdown - Dynamic" widget should meet your needs. Documentation in the readme is a little sparse/outdated right now so please use the descriptions of each widget parameter in the widget configuration itself. I'll be releasing this to the app store once I have a chance to update the documentation.