Form field with an explanatory pop up in flutter

I have a form in which I want to create a button like feature to explain the content of the form field. Something like this:

The question mark is the button itself, and when the user taps it, it shows a dialog or pop up (doesn't need to be like in the picture, but similar) which contains some text.

I was investigating about suffix property, that allows me to do something like that but not in the label text, as label text needs a string, not a widget, and its mandatory for this project to do this in the label text.

Here is the current code of that form field:

DropdownSearch<
            Map<String, dynamic>>(
          dropdownDecoratorProps:
              const DropDownDecoratorProps(
            dropdownSearchDecoration:
                InputDecoration(
              floatingLabelBehavior:
                  FloatingLabelBehavior.auto,
              labelText: "Crop",
              disabledBorder: InputBorder.none,
              hintText: 'Select crop',
            ),
          ),

          //Dropdown search items
        )

What you can do is add the button that you want to use to display the explanation, then you can wrap it a Tooltip widget like this:

                      Tooltip(
                                message:
                                    'Explanation here',
                                child: Icon(
                                    Icons.info,
                                  ),
                              )

The Tooltip is triggered by default upon a longPress but you can change this to be onTap, you can also change the duration that the message appears for, by doing the following:

                      Tooltip(
                                triggerMode: TooltipTriggerMode.tap,
                                showDuration: Duration(milliseconds: 5000),
                                message:
                                    'Explanation here',
                                child: Icon(
                                    Icons.info,
                                ),
                              )