I doubt that you would be able to find Cardinal Shrimp on this forum, or other similar for that even.
Try local club forum and hopefully get yourself in on a group buy or something.
We are currently having a Cardinal group buy here in Socal and if you wait I suppose some might be able to share once they breed and stuff.
Edit: I might have spoken too soon. Our group buy leader might sell some extra Cardinal over aquabid if the people fall through on the buy. Check it out on SCAPE. Cheers