Select2 User Select Add a new Company Popup Window

I have this Company control that list all the company from the database. I also added this Add a New Company... -1 which I would like the user to select if it is a new company that a pop up window will display and the user can enter the information. Any help would be great

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    html += "<h3 class='form-section'>Submission Information</h3><div class='row'>";
    html += "<div class='col-md-6'><div class='form-group'><label class='control-label'>Company</label>";
    
   html += "<select id='txtCompany' name='txtCompany' class='form-control select2-multiple' multiple='multiple'>";
    
    html += "<option value=''></option> <option value='-1'>Add a New Company...</option>";
    html += "<optgroup label = 'Existing Company' >";
    $.each(data.listOfRequesters, function (index, r) {
    if (requesterList.includes(r.SubmissionRequesterId)) {
       html += "<option value='" + r.SubmissionRequesterId + "' selected='selected'>" + r.Company + "</option>"
     } else {
    html += "<option value='" + r.SubmissionRequesterId + "'>" + r.Company + "</option>"
    }
    });
    
   html += "</optgroup></select>";