Getting Select2 Gem to work with ActiveAdmin "Add New" Button

I have a RubyOnRails Application that uses the ActiveAdmin and Select2 Gems. Right now, I have made a search box that after typing two letters, shows possible options from the set given. Here is the code for that:

f.has_many :location_permissions, :allow_destroy => true, heading: 'Users With Access To This Installation' do |app_f|
  app_f.input :user,  :input_html => { :class => "user_select" }, :collection => User.all.map{ |user| ["#{user.name} (#{user.email})", user.id] }
end

This also creates an "Add New" button below. When the button is clicked, a regular ActiveAdmin dropdown menu appears, but I want the Select2 search menu created above to show up. How do I do this?

Here is the user_select function:

$('.user_select').select2({
  minimumInputLength: 2
});

If I click the add new button, so it creates a new form, save that empty field, and then refresh the page, the new form becomes the Select2 search form I want. This leads me to think that Select2 applys its JS and CSS on page load, so is it possible to load that part of the page again through AJAX or some other mechanism? I have no idea how to do so, so if anyone could point me at a resource to do something like that, I would appreciate the help.

via Chebli Mohamed