My experience reinforces Diapositivo's comments - the MISTRAL was a good idea that suffered in execution. The plastic bag was flimsy and too small. It might be OK for a home darkroom with a single user, but it wasn't rugged enough for the continuous use that it received in the teaching darkroom where I encountered it. And the bag was too small for a situation where several dozen rolls of film were processed each day. Yes, it did dry film very quickly, but in a teaching situation, film is processed in large batches, and the size of the tent wouldn't accommodate all of the film produced by a class in a single session.
The other issue was that the heater got very warm. Now, it did dry film quickly, but I don't think it was necessary that the air be warmed quite as much as the MISTRAL was designed to do.
The unit that I saw is still in use in the teaching darkroom - the plastic bag was discarded, and replaced with a hard cabinet with a plexiglass door. In addition to being rugged, the cabinet provides more hanging space to handle a larger volume of film.
I don't know what discontinued MISTRALs sell for, but I do know that I built a film drying cabinet for a relatively modest amount. I made the cabinet from MDF with plexiglass glazing in the door. The fan is a computer-style muffin fan from Radio Shack. Air is drawn in to the top through a filter, and then passes through a second filter before entering the film chamber. I have a 200w incandescent lamp at the top of the chamber in the center of the air path to illuminate the interior and as a source of heat. Air exits the chamber through vents at the bottom. Film hangs from a rack that started life as a cut-off scrap of Cabinet Maid wire shelving. Film dries in about 30 minutes with the fan/light on, or about 4 hours with the fan/light off.