To make your own, simply screw a blower motor to plywood with some heavy base. Then attach a 4" PVC tube to the plywood with zip ties and screws. I used duct tape along the bottom of the tube for a better seal. Next cut out a section of the pipe for the loading chamber. Gorilla tape was used for the hinge and it works fine. I also taped a small section around the door opening on the inside of the tube for a better seal. Anything will do for the door handle. Obviously check for sharp edges or screws before letting the kids loose on it.
That's it, plug it in, load it up and have fun.
Here's a large video of it in action. And yes that is an instructables t-shirt my son is wearing.