Not possible. Ecommerce generally is not possible on WordPress.com. If the staff think your blog exists primarily to drive affiliate sales, they will disable your links. If you do one now and again it should be fine, but no, you can’t use any iframes here. Just use text links in your posts.
I have an issue listing my books from my amazon affiliate site, there are only 10 that i’ve recommended for my topic yet when i use the text widget to add the html from amazon to my sidebar it does not save and only appears as a link. http://www.thecreditgoddess.info
if you wouldn’t mind sharing how i can also submit the html? i just don’t want to see it in a post.