This plugin will let you retrieve all custom field info for use in stand alone entry forms or anywhere else. If the field has options there’s a variable pair for that. There’s no restriction on formatting either so you’re free to use it how you will.

The project is available on GitHub publicly, feel free to donate via Pledgie if you have the inclination!

Example usage for a text field

{exp:linssen_saef_field name="my_text_field"}
  <p><label for="{id}">{label}</label><br />
    <input type="text" name="{id}" id="{id}" value="" />
  </p>
{/exp:linssen_saef_field}

Example usage for a relationship field:

{exp:linssen_saef_field name="my_relationship_field"}
  <p><label for="{id}">{label}</label><br />
    <select name="{id}" id="{id}">
      {options}<option value="{value}">{name}</option>{/options}
    </select>
  </p>
{/exp:linssen_saef_field}