Yes, check on instructables.com - I'm pretty sure that is where I saw one.

Basically, there seem to be two DIY methods that use mirrors and laptops. I'm unsure as to the solution for timed scrolling, but I believe that most of the DIY methods include a manual scroll - someone's gotta do something... perhaps that's how it is in studios?

I know I have seen several boxen that people have done with lots of instructions online.

Oh, here's one of them:
http://www.instructables.com/id/EYS7FYANN0EV2Z3QGO/

Here's another:

http://www.wallstreetfreethinker.com/otherstuff/PlastiPrompter/plastiprompter.htm

I assume you've already seen those from googling...

Hope this is helpful and not just pointing at generic stuff.