Showconfig.aspx file exists in the CM server only by doing this you will be able to add this file in the CD server as well.
Add this file to the CD server.
<%@ Page language="c#" %>
<%@ Import namespace="System" %>
<%@ Import namespace="System.Xml" %>
<%@ Import namespace="Sitecore.Configuration" %>
<%
XmlDocument configuration = Factory.GetConfiguration();
Response.ContentType = "application/xml";
Response.Write(configuration.OuterXml);
%>