I'm writing an app that has an option to show pictures from SmugMug on another site, I use smugmug.images.getURLs to get the image URL and link to it from the other site and everything just works.
I want to add a buy link to the photos displayed on that site, I do not want to write a shopping cart or anythng like that - I just want a link to SmugMug that will let customers buy prints.
The site the pictures are displayed on is under my full control, I can change anything in the html, css, javascript and even in the backend.