Zen Cart custom option

I would like to add a feature on my site to be able to combine two product into one. features: from the product info page, customer can click on button "ADD A PRINT" that will allow a popup window to appear with all my print options. This could be done as an attribute or separate product that will be combined in the [login to view URL] print selection should be visible in the product info page. Please note that the "prints" will be used for many products, so I would like this to be an easy way to add this possibility to any product I choose. This is a link of an example web site. [login to view URL] my current site is [login to view URL]