Someone sells a light insert, maybe nano technology (like a printed board circuit rather than individual LED bulbs) like the Stern frames use, it's a kit for custom frames. Maybe it was spotlightdisplays? I first heard about them in a post by them on Pinside.
On second look, it was these guys:
This place has some interesting light boxes and this in particular sells just the actual box insert light panel.
https://www.blueriverdigital.com/lightboxes/LyteBlade-Econo-LED