Member only form

Site URL: http://datacircles.org

Hello all!

Our organization is made up of volunteers.  Each department has needs for other volunteers.  We are looking for a way to have a form that just the department heads can access to put in their job requests to the volunteer coordinator.  We like the functionality of sending the requests to a Google Sheet like that is available in Squarespace.  BUT we don't want to see it in the site's navigation and I don't want to make them have to type through security passwords to get to the form.  It needs to be as easy as possible.  I would love it if there were some kind of app/button on their phone that could take them directly to this form to fill out.  Does anyone know if that exists?  And how to do it if so?