http://www.scientificsonline.com/cardiac-illustrated-computation-aid.html
If you need some more background information, Wikipedia can help you:
http://en.wikipedia.org/wiki/CARDboard_Illustrative_Aid_to_Computation
It's listed as a clearance item and the price is $14 at the moment, which I think is a steal. Get a few and use them as gifts for your retro-computing friends.
Mike