The SmartMLS does not have a singular "Binder" form because there is no one form that is considered a binder. There are several different forms that can be used for the purpose of creating a binding agreement to purchase a property from a seller.
The most commonly used forms are the Purchase and Sale Agreement (two pages) and the Standard Form Real Estate Contract (4 Pages). Both of these forms are attached to this article.
Additionally, some offices create their own version of this form based off of one of these two forms. You may want to check with your office to see if they have their own version they prefer you use.