I found myndology flashcards several months ago at WalMart and thought they'd be good for swatches, so I got a pack. After trying them with several inks, I went back to buy more, and there was only one pack and no place on the shelf for them - so I figured they were gone and wasn't going to mention them, but today I found this:
Myndology flashcards
There are 75 cards per pack, sized 2 1/8" by 3 5/16" (5.4cm x 8.4cm). They're a bright white, about the thickness of card stock. They're smooth and take ink well. Only my worst-behaved inks showed a little feathering, the only show-through was where I laid the ink on really thick on one card. They show color and shading beautifully. Only one ink has shown sheen (Mont Blanc Leo Tolstoy Sky Blue LE), even though I've got Yama Dori and Robert Oster inks on there (they wanted to sheen, if you know what I mean, but couldn't quite do it).
Here's some of my use over the past several months:
Anywho, I haven't seen them mentioned recently and a search made me think it's been years, so I thought I'd let you know you may find them at your local WalMart (or not). On the back of the pack is a website, but I couldn't find these cards on that site.