Edit "product short description"

Hello,

I am trying to add some code unique to each individual “product short description” without having to go into each product individually. Is there a way to add something to the custom CSS section for the theme?

I am an Amazon affiliate, and I want to insert the following into each “product short description”:
<div class=”buy-now”>XXXXXXXXXX” target=”_new”>Buy Now</div>

And I want the XXXXXXXXXX to grab the ASIN unique to each individual product.

This is normally achieved automatically by setting the “product data” type to “external/affiliate” instead of “simple”, but I have a plugin that will not work unless the products are “simple”.

Any thoughts?

Thanks,

Patrick