Last year I made my own komboloi. It is made from glass beads that I made to look like different type of natural material: wood, bone, amber, coral, turquoise, etc.
I should restring it, and make the string longer. The major difference, so it seems, between most prayer beads and the komboloi is that the komboloi has more string than is covered with beads. This is so you can toss them, and play with them. Prayer strands usually are fully covered.