I just found these ones with names...scroll down just past the label
She used Shrinky Dink Paper? I have never heard of it. I looked it up and you print on it with an ink jet printer, put it in the oven and it shrinks and turns into hard plastic.... ummm... COOL!
SKP1 maybe this would work for you? Just print a bit bigger, since they already look great and let them shrink down? I think using card stock, if they get wet they will be ruined, which would be a shame, since you took the time to make them.
I think I might try this. If it works maybe I'll make some extra ones to put at the tables as favors. I saw some that were the word Party in different languages that I've been trying to figure out how to work in....