So far I have been unsuccessful at sourcing the postcards that are used to do Etegami on. I can find the cards on-line, but the postage to Canada is two or three times the value of the cards.
The special cards have various levels of "bleed" which help to make the ink and watercolor uncontrollable. (Ha! Maybe I'm out of control enough without additional help!)
I've been trying various kinds of cardstock to try and find ones that bleed. So far without success. In addition, with large areas of watercolor, the cardstock buckles. They really are too flimsy to mail, but they flatten out if pressed or ironed. Here's another; this one is a bit more creamy in colour: