Insert blocker inside another parent beside body

Is there away to have the modal blocker be positioned absolute in a relative container?

Here is what I have so far.
https://codepen.io/JacobLett/pen/mddOdmx?editors=1111

The line I need to adjust somehow
this.$blocker = $('<div class="' + this.options.blockerClass + ' blocker current"></div>').appendTo(this.$body);

thank you for any help you can provide.