While they are sometimes available at places like Michael's or Shipwreck Beads, I've often resorted to making them myself by intertwining DMC embroidery floss around two strands of C Lon cording like these:
The "Rooster of Love" sits on a handmade Chinese knot made of DMC floss, the Dreamy Mermaid's resting place is a store bought knot found at a Michael's, and the Mouse is perched on a handmade Chinese knot.
