To create this widget you need to select a Custom widget (the last widget in the dropdown add widget menu)
Segment: Organic Traffic
Dimension: Month of the Year (for example)
Metric: goal Completions All
You can choose to track all goals completion.
Or you can choose to track organic traffic for specific goals:
In step 2, you can edit the widget title, widget description, you can choose the format and size of your GA widget:
During the last step, you can choose to hide metric or metric's change: