Need plugin for SmartMag or simple coding

Hi: I’m using SmartMag for my site and I’m not a technical person. Is there a plugin that will place a widget in each post (separate from the menu widget) that will allow me to add advertising specific to the content of each post? In other words, I would like to just be able to edit a post, go to a widget that’s on the sidebar and enter product html or links to affiliates. I have a lot of posts and I’d really appreciate a plugin recommendation from you experts. Thanks a lot for any help you can give me.