Jerry Mentzer's Magic Methods Online Magic Shop has sold this for years at http://www.magicmethodsonline.com/cmagic.html
CASCADE by Roy Walton This is another "goodie" from Roy Walton whose trick "Cardwarp" took the magic world by storm! In this effect, "Cascade", four cards turn face up, then face down in a most remarkable manner. At the finish of the effect, the performer shows he has been using trick cards- two have blank faces and two others have gaudy colored backs!! And the cards can be examined! They are indeed strange, but not gimmicked. If you can do an Elmsley count, this is an excellent effect to carry with you. Use the four cards as "covers" for your favorite coin assembly after performing "Cascade". SKILL LEVEL-Experienced/Medium PRICE-$5.00
Note: Firefox can't handle the text on his webpages. It's always been one of the most low-tech sites out there but something happens in Firefox. It looks fine in Internet Explorer.
Another note: I've been performing "Cascade" regularly for over 25 years and I would not want to use borderless cards, as shown in the pic on this webpage. This may be a good source for the instructions, but I'd be on the lookout for different, white-bordered cards.
Good luck! It's a great trick! Lots of variations out there but this is still excellent itself.