One way that you could do this would be to set a parameter for the item, like it's id in the link that the customer is going to click on. So the link might look like this:
This link should then direct the user back to a special page that you will make that will filter a recordset on the item id from the link. You can then use this filtered rs bindings for the add to cart server behavior that is on this page. You then just need to specify the checkout cart page as the redirect in the add to cart server behavior.