I stumbled across this solution to add attributes to the read more links of a node.
Using Ubercart's hook_product_description_alter() function to Update the cart_view_form and cart_checkout_form
I'm in the process of building a custom Ubercart module that allows users to dynamically enter sizes using Ubercart's uc_attributes module. The problem I ran into is that I needed to theme these custom attributes in the cart_view_form and cart_checkout_form to add a suffix behind value. Initially I overwrote the original theme file in my module using the phptemplate_ prefix. This worked great, however, after further consideration I realized the flaw in this logic. Overriding the theme like this would not allow other user's to override that theme file. So back to the drawing board I went.