We'll create fresh WordPress site with End Content installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plug-in allows you to add code such as a PayPal donate button to end of a post or page.
You can select certain post categories or certain pages to show the content or have it shown on all content.
Support is provided at http://www.thefunkhouse.co.uk/wordpress-plugins/end-content