I'm starting a print estore based on templates and have the option for two-sided printing, so after a customer chooses their front image and have added it to cart, if they have selected the 2-sided attribute, ideally I think I'd like them to be redirected to choosing the back "product" to add to cart for $0.

I considered adding this as another attribute option, but I plan to have about 50 or so back templates to choose from, so it would be a little silly to do it that way.

Looking for any suggestions anyone may have.

Testing at http://www.wholesale4realtors.com/cart
Using Zen3.8, modified default template, no major mods added.