The one Doug sells is the ONLY ONE being legally marketed that's based on the original Dick Zimmerman set-up, last I heard Dick was still making one specific piece that goes to the prop because of some
proprietary secrets that are involved with the materials.
There are however 101 methods of accomplishing what is essentially CONFABULATION and 99% of them involve that secret someone that does that hidden something in order to make you look like a master prognosticator. I am quite grateful that you distinguished the idea behind quality vs. price. . . this is an effect/system that you really don't want to cut corners on simply because it is presented as a BIG DEAL and thus, it must be 110% reliable. That said, does it have to be a box hanging in the air, why couldn't it be a large envelope?
For roughly $100.00 you could make-up the Sylvester the Jester version to this effect and I can assure you, it will make magician's drop their jaws. I've used this system on and off for over a dozen years and I believe the guy that shared it with me (Kevin James) is still using it as well; it is pure dynamite and bloody awful simple.
I'd be more than glad to help you with insights around the various methods and presentational facades that are out there if it would help you in your decision making process.
