Any suggestings for Amazon Linking for Contributing Writers?

I'm wondering if anyone has a plugin to suggest that would allow us to enter our amazon affiliate userID as a default and then our writers having the option to enter theirs, and then appropriate shortcoding or whatever in adding links to products, as a way for our writers to earn revenues. At the very least, a plugin that will link items with our (the publisher) userID?

I've tried out the plugin at http://wordpress.org/plugins/amazon-link/ but wasn't able to find a place to enter our Affiliate Username, nor was I able to find a place where our writers can enter their unique Affiliate username.