There has been one buried in the WSTK (http://www.alphaworks.ibm.com/tech/webservicestoolkit) since version 3.2, where it is used in the client side of the SLA subscenario of the utilityServices demo. You will find the load generator at WSTK_HOME/wsst/build/. What you will not find is usable documentation. That will appear in the next WSTK release (hopefully later this month).
Mike
