None that aren't super expensive. Check your LFS for any in the display tanks, and ask around local areas to see if anyone can give or sell you some. There are two types, black and white. White get about an inch wide (counting legs), and reproduce in big surges before dying off a bit sometimes. Black are actually sort of banded if you look up close, get about 2 inches wide, and reproduce more slowly but steadily. Both are great to have. A mix would be ideal.
These guys don't ship well priority mail. They really need to be sent overnight.