Have you tried looking on Craigslist? As long as they're no more than two weeks apart, they should be okay. Pyrrhos was a week and a half before we added three-day-old ducklings.
I completely missed that in your original post. I just Googled them haha. Pretty ducks!
EDIT:
Niacin! Ducklings...
Awww! (: What a cutie. He /looks/ about three or four days old(but I'm no expert, and the five ducks I have now are my first). I highly suggest getting duck feed(corn-free, as aflatoxin is a concern in corn now). Although you definitely don't have to, Azure Standard sells Peck and Scratch...