These were made from two 6-light fixtures from Home Depot and coroplast. Here's a spreadsheet I used to gather parts.
https://docs.google.com/spreadsheet/ccc?key=0Ap6oMFKAB1-4dHRhNzgtbVdtRTFNZzBLNU5QZVZBVlE#gid=1

https://docs.google.com/spreadsheet/ccc?key=0Ap6oMFKAB1-4dHRhNzgtbVdtRTFNZzBLNU5QZVZBVlE#gid=1

