If you can not find a place to purchase a CARDIAC there are a couple of places on the intertubes that will help you diy one up. Kyle Miller's page not only has all the pages you need to print to do this but also a PDF of the original manual.
One of the nice things about the plain layout is, if you need to hook the interest of the younglings or even old pheezers, you can customize them with a few simple machinations in GIMP or whatever your image manipulator of choice is. For my younger son, age 8 now, I am planning on a Pokemon skinned CARDIAC.
Other mods for the CARDIAC? Yes, yes indeed what the world needs now is CARDIACMODWORKS (tip of the hat to Cyanogen). Post up your mods here.
So there you go....print print snip snip paste paste and you are on your way to THE COMPUTER AGE!!! Sorry about that, it is exciting though.