I built a light box that wasn't nearly as nice as this one but easier to build and did the job. It was basically just a rectangular plywood box with no bottom and was open on the two long sides, plywood on the two ends, about 8-10 inches high. I attached the light fixtures underneath the top, the lack of sides allowed enough ventilation without the need for fans, and I had a lot fewer lights than this one - three fixtures, six lights I think (it's a little surprising how well the fixtures spread the light evenly despite being pretty close to the printing frame). I didn't find a need for reflective lining though that's a nice touch.

The lights were bought at a local light specialty store, the fixtures and plywood at Home Depot. Since the two long sides were open I could just slide the printing frame in and out without needing hinges. Total cost was probably about $100 or less, took an afternoon to build (with help from someone who knew more about electrical fixtures than I did) and worked well for the Van Dyke brown gum printing that I used it for.

If I was a more talented woodworker/electrician I would like to have had something as nice as the OP's but the one I had did the job and sure made printing times more predictable than using natural light.