edit Canonical url in IIS

I am using NopCommerce 3.7 with a plugin for affiliates.  The issue I am running into is Google is seeing each affiliate page as a duplicate link.  When I enable Canonical urls, the url produced is not the base url.
Examples -

Here is what I want the canonical url to be whether there is a affiliate or not.

<link rel="canonical" href="http://metest.mebulbs.com/a/cd/p1x135" />

Here is what the plugin produces if there is a affiliate-

<link rel="canonical" href="http://metest.mebulbs.com/a/joeblow/p1x135" />

Is it possible to write a rule in IIS to replace anything after the "/a/" and before the last "/" with "cd" ?

If I can do this as page is being published, Google will see the default page and ignore all the duplicate affiliate pages.

You might as well hardcode this in the View?

Which file would that be?  It's not totally a hard coded string, I need to append whatever product link browser is going to.

The /cd/ in actually defined as a default affiliate.

Attempting to use All in One widget to put java script in to make canonical link.

<p id="gcanonical">&nbsp;</p>
<p>
<script>// <![CDATA[
var a = window.location.href;
var b = a.split("/");
var c = b[3];
var d = '<link rel="canonical" href="http://metest.mebulbs.com/a/cd/' + c + '"/>'
alert(c);
alert(d);
document.getElementById("gcanonical").innerHTML = d;
// ]]></script>
</p>

The alerts show the proper strings in var's, but when view source is used, the finished var does not appear.

What am I missing?

View Source shows unprocessed source. If you want to see the DOM after JS has run, use Inspect in Chrome.

And I am not sure if Google will consider adding canonical tag using JS.

http://searchengineland.com/tested-googlebot-crawls-javascript-heres-learned-220157

Info on Google & js