I happen to have one! Send me $100 and I'll ship it to you. Oh hell, you sound like a nice guy...make it $75. It was previously owned by a little old lady who only used it to go to church on sundays.
I actually caught myself wanting to believe Robert Zemeckis when he so casually indicated that they are real in a behind the scenes interview. Reality Check Actual Movie Props
Get a long extension cord, and this is pretty fun. AirSled
Direction control isn't really it's strong suite, and it's a bit loud, but hey it does work. I actually tried one that last time we had our refrige installed. I skated all around my kitchen. I would avoid any sloping grades. Its' not pretty.
And finally, The Airboard The QT Videos are cute. A bit reminiscent of those cheesy Segway HT Clips.